Tuber and Tuberous Root Development

Regulation of storage organ formation by long-distance tuberigen signals in potato

Potatoes are valued as reliable crops due to their high carbohydrate content and relatively low farming demands. Consequently, significant attention has been directed towards understanding and controlling the life cycle of potato tubers in recent years. Notably, recent studies have identified self-pruning 6A (StSP6A) as a key component of the tuberigen, the mobile signal for tuber formation, produced in leaves and then transported underground to induce tuber formation in potatoes. Recent progress in comprehending the signaling mechanisms that regulate StSP6A by photoperiod and ambient temperature components, its long-distance transport into underground tissue, and its involvement in regulating stolon tuberization has advanced significantly. Consequently, the modulation of StSP6A and other possible tuberigen signals, along with their regulatory pathways, significantly impacts potato domestication and crop yield. This progress highlights the differential regulation of tuberigen signals and their potential functions in promoting tuber formation.

Do storage reserves contribute to plant phenotypic plasticity?

The widespread colonization of diverse habitats by plants is attributed to their ability to adapt to changing environments through environmental phenotypic plasticity. This flexibility, particularly in carbon turnover, allows plants to adjust their physiology and development. Plants store carbon reserves as a metabolic strategy to overcome adversity, with a variety of isozymes evolving to enhance metabolic plasticity. Among these isoforms, some with entirely new functions have emerged, involved in novel metabolic pathways for carbon storage. Here, we discuss the role of these carbon stores, their impact on plant plasticity, methods by which such metabolic plasticity can be analyzed, and evolutionary aspects that have led to well-characterized as well as less well-known molecular mechanisms underlying carbon storage.

The PteridoPortal: A publicly accessible collection of over three million records of extant and extinct pteridophytes

Premise

Pteridophytes-vascular land plants that disperse by spores-are a powerful system for studying plant evolution, particularly with respect to the impact of abiotic factors on evolutionary trajectories through deep time. However, our ability to use pteridophytes to investigate such questions-or to capitalize on the ecological and conservation-related applications of the group-has been impaired by the relative isolation of the neo- and paleobotanical research communities and by the absence of large-scale biodiversity data sources.

Methods

Here we present the Pteridophyte Collections Consortium (PCC), an interdisciplinary community uniting neo- and paleobotanists, and the associated PteridoPortal, a publicly accessible online portal that serves over three million pteridophyte records, including herbarium specimens, paleontological museum specimens, and iNaturalist observations. We demonstrate the utility of the PteridoPortal through discussion of three example PteridoPortal-enabled research projects.

Results

The data within the PteridoPortal are global in scope and are queryable in a flexible manner. The PteridoPortal contains a taxonomic thesaurus (a digital version of a Linnaean classification) that includes both extant and extinct pteridophytes in a common phylogenetic framework. The PteridoPortal allows applications such as greatly accelerated classic floristics, entirely new "next-generation" floristic approaches, and the study of environmentally mediated evolution of functional morphology across deep time.

Discussion

The PCC and PteridoPortal provide a comprehensive resource enabling novel research into plant evolution, ecology, and conservation across deep time, facilitating rapid floristic analyses and other biodiversity-related investigations, and providing new opportunities for education and community engagement.

Low light reduces saffron corm yield by inhibiting starch synthesis

The mechanisms by which low light modulates source-sink dynamics, affecting starch synthesis and formation of underground storage organs in geophyte, remain unclear. In this study, a two-year field experiment was conducted under natural light (NL) and low light (LL, 50% of NL intensity) conditions. LL resulted in a 23.66% and 21.23% reduction in corm yield in 2023 and 2024, respectively. Saffron plants under LL had larger, longer leaves with a higher proportion of dry weight (DW) compared to those under NL. Despite the marked inhibition of photosynthetic capacity, initial DW, sucrose and glucose concentrations in leaves were comparable to those under NL. Carbohydrate analysis revealed that starch concentration in the mother corms under LL decreased by 18.00% relative to NL, while sucrose and glucose concentrations increased by 28.44% and 68.44%, respectively. At the corm expansion stage, sucrose concentration in leaves and daughter corms under LL conditions was 17.32% and 54.08% higher than under NL, but glucose and starch concentrations in daughter corms were 22.08% and 10.22% lower, respectively. Additionally, the activity of invertase (INV), sucrose synthase in the decomposition direction (SUS) and ADP-glucose pyrophosphorylase (AGPase) in daughter corms were reduced under LL. LL also affected phytohormones concentrations, with increased levels of indole-3-acetic acid (IAA) and gibberellin (GA1) in LL leaves and daughter corms, and decreased abscisic acid (ABA) levels. Transcriptome and quantitative PCR analyses showed that LL upregulated the expression of genes involved in glycolysis and the tricarboxylic acid cycle in leaves, while downregulating CsSUS, CsINV1, CsAGPS1, CsZEP, and CsNCED, which are key to sucrose hydrolysis, starch synthesis, and ABA biosynthesis. Exogenous GA3 application further inhibited SUS, INV and AGPase activities in daughter corms, indicating that high GA concentrations impair carbohydrate metabolism in these organs. In conclusion, LL decreases saffron corm yield by promoting the allocation of reserves from mother corms to leaves at the seedling stage. By the period of the daughter corms enlargement, elevated GA1 and IAA levels and reduced ABA concentration promote leaf growth while inhibiting carbohydrate metabolism in daughter corms, thereby reducing sucrose transport from leaves to daughter corms and suppressing corm yield formation.

Evolutionary analysis of DELLA proteins in sweet potato and related species reveals their roles in development and stress responses

DELLA proteins act as master negative regulators in the gibberellin signaling pathway, which controls numerous aspects of plant growth and development. Despite the pivotal role of DELLA proteins, a comprehensive genome-wide analysis of the DELLA gene family in sweet potato (Ipomoea batatas) and its related species has yet to be conducted. Here, we performed a comparative analysis of this gene family among six Ipomoea species, including Ipomoea batatas, Ipomoea trifida, Ipomoea triloba, Ipomoea nil, Ipomoea cairica, and Ipomoea aquatica. Among the six Ipomoea species, only I. nil contains five DELLA genes, while the remaining species have three DELLA genes each. The DELLA genes were categorized into three distinct subgroups based on the phylogenetic topology in selected Ipomoea species. Comparative analysis of gene structure and protein motifs revealed that members within the same phylogenetic group exhibit comparable exon/intron and motif organization. The cis-regulatory elements of the DELLA gene in selected Ipomoea species contain unique promoter elements, indicating the presence of species-specific regulatory mechanisms. A multitude of shared cis-regulatory elements related to stress responses were identified in the DELLA gene promoters. Furthermore, a syntenic analysis indicates two groups of syntenic DELLA genes have undergone several rearrangements. The results of the duplication analysis indicated that dispersed duplications contribute to the expansion of the DELLA genes. Moreover, the DELLA genes in sweet potato display an expression pattern that tends to control the growth and development of either the aerial or below-ground parts, and they are responsive to a range of hormones and abiotic stresses. Thus, these findings provide insights into the evolutionary history of DELLA genes within the genus Ipomoea and the functions of sweet potato DELLA genes.

Carotenoids in Potato Tubers: A Bright Yellow Future Ahead

Carotenoids, the bright yellow, orange, and red pigments of many fruits and vegetables, are essential components of the human diet as bioactive compounds not synthesized in animals. As a staple crop potato has the potential to deliver substantial amounts of these nutraceuticals despite their lower concentration in tubers compared to edible organs of other plant species. Even small gains in tuber carotenoid levels could have a significant impact on the nutritional value of potatoes. This review will focus on the current status and future perspectives of carotenoid biofortification in potato with conventional breeding and biotechnological approaches. The high biodiversity of tuber carotenoid levels and composition is presented, with an emphasis on the under-exploited native germplasm that represents a wide reservoir of useful genetic variants to breed carotenoid-rich varieties. The following section describes the structural genes involved in carotenoid metabolism and storage known to have a major impact on carotenoid accumulation in potato, together with the strategies that harnessed their expression changes to increase tuber carotenoid content. Finally, the little information available on the regulation of carotenoid metabolism and the desirable future advances in potato carotenoid biofortification are discussed.

Mutation of MeMinD increased amyloplast size with a changed starch granule morphologenesis and structures in cassava storage roots

Amyloplasts are the sites of starch synthesis and accumulation. Little is known about amyloplast division and its effects on the size, structure, and physicochemical properties of starch granules. In this study, we created mutants of plastid division-related gene MeMinD by CRISPR/Cas9 technology, leading to the disruption of normal division of amyloplasts in cassava storage roots. The memind mutants exhibited significantly enlarged amyloplasts with an increased number of starch granules, and broader range of granule sizes. The loss of MeMinD function led to transcriptional reprogramming of gene expressions related to starch-synthesizing enzymes, affecting the fine structure of starch. Starch in memind mutant storage roots showed a significantly decreased proportion of shorter amylopectin chains and an increased proportion of medium and long chains, which ultimately led to a significant increase in apparent amylose content (AAC) in memind mutants compared to that in WT. The changes in starch granule size and structure resulted in a significant increase in onset temperature (To), peak temperature (Tp), and conclusion temperature (Tc) of the gelatinization process, extending the time to reach peak temperature. These data suggest that regulating amyloplast division affects starch accumulation in cassava, presenting an effective strategy for developing novel cassava starch.

Metabolic and transcriptional analysis of tuber expansion in Curcuma kwangsiensis

The tubers of Curcuma kwangsiensis are regarded as an important medicinal material in China. In C. kwangsiensis cultivation, tuber expansion is key to yield and quality, but the regulatory mechanisms are not well understood. In this study, metabolomic and transcriptomic analyses were conducted to elucidate the mechanism underlying tuber expansion development. The results showed that auxin (IAA), jasmonic acid (JA), gibberellin (GA3), ethylene (ETH), and brassinolide (BR) levels increased during tuber expansion development. Metabolomic analysis showed that 197 differentially accumulated metabolites (DAMs) accumulated during tuber expansion development and these also play important roles in the accumulation of carbohydrates and secondary metabolites. 6962 differentially expressed genes (DEGs) were enriched in plant hormone signal transduction, starch and sucrose metabolism, linoleic acid metabolism, MAPK signaling pathway as well as sesquiterpenoid and triterpenoid biosynthesis. Comprehensive analysis revealed that DEGs and DAMs of plant hormone signal transduction, ABC transporters and biosynthesis of phenylpropanoids and terpenoids are critical pathways in regulating tuber expansion. In addition, some transcription factors (ARF, C2H2, C3H, NAC, bHLH, GRAS and WRKY) as well as hub genes (HDS, HMGR, ARF7, PP2CA, PAL and CCOMT) are also involved in this process. This study lays a theoretical basis for the molecular mechanism of tuber expansion in C. kwangsiensis.

The giant genome of lily provides insights into the hybridization of cultivated lilies

Lilies are economically important monocots known for their ornamental flowers, bulbs, and large genomes. The absence of their genomic information has impeded evolutionary studies and genome-based breeding efforts. Here, we present reference genomes for Lilium sargentiae (lily, 35.66 Gb) and Gloriosa superba (flame lily, 5.09 Gb). The giant lily genome is shaped by recent long terminal repeat retroelements. Phylogenetic analysis reveals diverse, independent origins of lily cultivars. Gene families involved in sucrose and starch metabolism are significantly expanded in the lily genome. Key homologs of XTH22, SOC1, and AP1/FUL-like genes regulate the development, bud growth transition, and floral bud growth transition of lily bulbs. Colchicine biosynthetic gene clusters are identified in G. superba but are absent in L. sargentiae, highlighting independent colchicine evolution in Colchicaceae. These genomic insights enhance understanding of Liliales evolution, providing a foundation for future breeding and molecular research.

The link between changing in host carbon allocation and resistance to Magnaporthe oryzae: a possible tactic for mitigating the rice blast fungus

One of the most destructive diseases affecting rice is rice blast, which is brought on by the rice blast fungus Magnaporthe oryzae. The preventive measures, however, are not well established. To effectively reduce the negative effects of rice blasts on crop yields, it is imperative to comprehend the dynamic interactions between pathogen resistance and patterns of host carbon allocation. This review explores the relationship between variations in carbon allocation and rice plants' ability to withstand the damaging effects of M. oryzae. The review highlights potential strategies for altering host carbon allocation including transgenic, selective breeding, crop rotation, and nutrient management practices as a promising avenue for enhancing rice blast resistance. This study advances our knowledge of the interaction between plants' carbon allocation and M. oryzae resistance and provides stakeholders and farmers with practical guidance on mitigating the adverse effects of the rice blast globally. This information may be used in the future to create varieties that are resistant to M. oryzae.

The physiological and molecular responses of potato tuberization to projected future elevated temperatures

Potato (Solanum tuberosum L.) is one of the most important food crops globally and is especially vulnerable to heat stress. However, substantial knowledge gaps remain in our understanding of the developmental mechanisms associated with tuber responses to heat stress. This study used whole-plant physiology, transcriptomics, and phytohormone profiling to elucidate how heat stress affects potato tuber development. When plants were grown in projected future elevated temperature conditions, abscisic acid (ABA) levels decreased in leaf and tuber tissues, whereas rates of leaf carbon assimilation and stomatal conductance were not significantly affected compared to those plants grown in historical temperature conditions. While plants grown in projected future elevated temperature conditions initiated more tubers per plant on average, there was a 66% decrease in mature tubers at the final harvest compared to those plants grown in historical temperature conditions. We hypothesize that reduced tuber yields at elevated temperatures are not due to reduced tuber initiation, but due to impaired tuber filling. Transcriptomic analysis detected significant changes in the expression of genes related to ABA response, heat stress, and starch biosynthesis. The tuberization repressor genes SELF-PRUNING 5G (StSP5G) and CONSTANS-LIKE1 (StCOL1) were differentially expressed in tubers grown in elevated temperatures. Two additional known tuberization genes, IDENTITY OF TUBER 1 (StIT1) and TIMING OF CAB EXPRESSION 1 (StTOC1), displayed distinct expression patterns under elevated temperatures compared to historical temperature conditions but were not differentially expressed. This work highlights potential gene targets and key developmental stages associated with tuberization to develop potatoes with greater heat tolerance.

Multiomics joint analysis reveals the potential mechanism of differences in the taproot thickening between cultivated ginseng and mountain-cultivated ginseng

Panax ginseng is an important medicinal plant in China and is classified into two types: cultivated ginseng (CFCG) and mountain-cultivated ginseng (MCG). The two types of genetic varieties are the same, but the growth environments and management practices are different, resulting in substantial differences in their taproot morphology. Currently, there is a paucity of research on the internal mechanisms that regulate the phenotypic differences between cultivated ginseng and mountain-cultivated ginseng. In this study, we explored the potential mechanisms underlying their phenotypic differences using transcriptomic and metabolomic techniques. The results indicate that the taproot thickening of CFCG was significantly greater than that of MCG. Compared with MCG-4, MCG-10, and MCG-18, the diameters of the taproots of CFCG-4 increased by 158.96, 81.57, and 43.21%, respectively. Additionally, the contents of sucrose and starch in the taproot, as well as TRA and DHZR, were markedly elevated. Transcriptome analysis revealed that compared with MCG of different age groups, genes associated with starch and sucrose metabolism pathways (PgSUS1, PgSPS1, PgSPS3, and PgglgC1) were significantly upregulated in CFCG-4, whereas genes involved in the phenylpropanoid biosynthesis pathway (PgPER3, PgPER51, and PgPER12) were significantly downregulated in CFCG-4. This imbalance in the metabolic pathways suggests that these genes play crucial roles in ginseng taproot thickening. PgbHLH130 and PgARF18 may be key regulators of transcriptional changes in these pathways. These findings elucidate the molecular mechanisms governing ginseng taproot thickening, and have important implications for enhancing the overall quality and value of ginseng.

Unlocking epigenetic breeding potential in tomato and potato

Tomato (Solanum lycopersicum) and potato (Solanum tuberosum), two integral crops within the nightshade family, are crucial sources of nutrients and serve as staple foods worldwide. Molecular genetic studies have significantly advanced our understanding of their domestication, evolution, and the establishment of key agronomic traits. Recent studies have revealed that epigenetic modifications act as "molecular switches", crucially regulating phenotypic variations essential for traits such as fruit ripening in tomatoes and tuberization in potatoes. This review summarizes the latest findings on the regulatory mechanisms of epigenetic modifications in these crops and discusses the integration of biotechnology and epigenomics to enhance breeding strategies. By highlighting the role of epigenetic control in augmenting crop yield and adaptation, we underscores its potential to address the challenges posed by a growing global population as well as changing climate.

The molecular coordination of tuberization: Current status and future directions

The integration of bulk transcriptomic, proteomic, and genomic data generated from numerous systems biology studies of tuberizing plants has resulted in a better understanding of the molecular and morphological aspects of tuberization. The identified conserved integrated hormonal, transcriptional, and metabolic pathways of tuberization in crops from various plant lineages support the hypothesis of a fundamental tuberization process. However, further studies are required to specify the additional processes defined by the genomics and phylogeny of the particular plant lineages, which control the morphological diversity of tubers. This review summarizes the latest molecular and morphological discoveries on the tuberization process in stem tubers and tuberous roots and discusses future trajectories of the field.

Deciphering the Effects of Phosphate Fertiliser on Rhizospheric Bacterial Community Structure and Potato Common Scab

The prolonged practice of continuous potato cropping, coupled with inadequate field management, disrupts the soil bacterial community equilibrium. Such disturbances compromise the resilience of the soil ecosystem, predisposing it to an increased incidence of potato diseases. However, the effects of the phosphorus fertiliser application rate on the rhizosphere soil bacterial community composition of potatoes and the occurrence of potato common scab (CS) have not been adequately studied. Here, diseased field soils from Dingxi and Huidong Counties were collected for potting tests, and field tests were conducted in Huidong County for validation. An examination of the relationship between the bacterial community composition in the potato rhizosphere soil and potato CS under different phosphate fertiliser treatments was conducted using 16S rRNA high-throughput sequencing. The results show that a lower phosphorus fertiliser application rate was more conducive to maintaining soil bacterial community diversity under different phosphorus fertiliser treatments in different habitats. In addition, the relative abundance of the txtA gene increased significantly (p < 0.05) with the increase in the phosphate fertiliser application rate. Field trials conducted in Huidong revealed that treatments F1, F2, and F3 had respective CS incidence rates of 28.33%, 46.67%, and 59.44%, while their corresponding disease severity indices were 7.67, 17.33, and 29.44. Further analysis revealed that the relative abundance of antagonistic genera of pathogenic S. scabies decreased significantly (p < 0.05) with increases in the phosphorus fertiliser application rate. In summary, the correlation between potato CS and changes in the bacterial community of rhizosphere soil was used to determine the optimal phosphorus application rate during potato production, which can provide a scientific basis for the management of phosphorus fertiliser in potato farmland.

Structure and physicochemical properties of starches from six accessions of the genus Pueraria in China

Kudzu (Pueraria lobata) root contains abundant starch, but the physicochemical properties of kudzu starch are not well understood. In this study, we compared the compositions and physicochemical properties of starches isolated from six Pueraria accessions in China. Caige starch exhibited the highest purity (96.99 %) and amylose content (24.76 %), while Yege starch contained higher levels of puerarin (493.37 μg/g) and daidzein (38.68 μg/g). All kudzu starches were rich in resistant starch, with RS2 content ranging from 38.61 % to 46.22 % and RS3 content from 3.59 % to 6.04 %. The granules of kudzu starches varied in morphology, with Yege starch featuring larger polygonal granules. The kudzu starches presented either A-type or A-type-like C-type diffraction patterns. Caige starch had a higher IR2 value (1.28), higher gelatinization temperatures, wider temperature ranges, and greater enthalpy changes. Yege (JX) starch exhibited the highest peak viscosity but the lowest setback viscosity and pasting temperature. Fenge starch showed the highest final viscosity, with Fenge (ZJ) starch demonstrating the highest crystallinity (25.7 %) and IR1 value (0.80). These results indicated that kudzu starches derived from various Pueraria species possess unique structural and physicochemical properties, which provide significant potential for applications in food and other industrial fields.

Preparation, bioactivities, and food industry applications of tuber and tuberous roots peptides: A review

Tuber and tuberous roots proteins are important sources for producing bioactive peptides. The objective of this review is to present the current research status of tubers and tuberous roots bioactive peptides (TTRBP), including its preparation methods, purification techniques, structure identification approaches, biological functions, and applications in the food industry. Moreover, the current challenges and future development trends of TTRBP are elucidated. Currently, TTRBP are mainly produced by enzymatic hydrolysis and fermentation. Pretreatment like high static pressure, ultrasound and microwave can assist enzymatic hydrolysis and facilitate TTRBP production. In addition, TTRBP are structurally diverse, which is related to the molecular weight, amino acids composition, and linkage mode. Accordingly, they have various biological activities (such as antioxidant, antihypertensive, hypoglycemic) and have been utilized in the food industry as functional ingredients and food additives. This review will provide valuable insights for the optimal utilization of tuber and tuberous roots.

KIN10-mediated HB16 protein phosphorylation and self-association improve cassava disease resistance by transcriptional activation of lignin biosynthesis genes

Cassava bacterial blight significantly affects cassava yield worldwide, while major cassava cultivars are susceptible to this disease. Therefore, it is crucial to identify cassava disease resistance gene networks and defence molecules for the genetic improvement of cassava cultivars. In this study, we found that MeHB16 transcription factor as a differentially expressed gene in cassava cultivars with contrasting disease resistance, positively modulated disease resistance by modulating defence molecule lignin accumulation. Further investigation showed that MeHB16 physically interacted with itself via the leucine-Zippe domain (L-Zip), which was necessary for the transcriptional activation of downstream lignin biosynthesis genes. In addition, protein kinase MeKIN10 directly interacted with MeHB16 to promote its phosphorylation at Ser6, which in turn enhanced MeHB16 self-association and downstream lignin biosynthesis. In summary, this study revealed the molecular network of MeKIN10-mediated MeHB16 protein phosphorylation improved cassava bacterial blight resistance by fine-tuning lignin biosynthesis and provides candidate genes and the defence molecule for improving cassava disease resistance.

Evolution of the sporophyte shoot axis and functions of TALE HD transcription factors in stem development

The stem is one of the major organs in seed plants and is important for plant survival as well as in agriculture. However, due to the lack of clear external landmarks in many species, its developmental and evolutionary processes are understudied compared to other organs. Recent approaches tackling these problems, especially those focused on KNOX1 and BLH transcription factors belonging to the TALE homeodomain superfamily have started unveiling the patterning process of nodes and internodes by connecting previously accumulated knowledge on lateral organ regulators. Fossil records played crucial roles in understanding the evolutionary process of the stem. The aim of this review is to introduce how the stem evolved from ancestorial sporophyte axes and to provide frameworks for future efforts in understanding the developmental process of this elusive but pivotal organ.

Contribution of homoeologous exchange to domestication of polyploid Brassica

BACKGROUND

Polyploidy is widely recognized as a significant evolutionary force in the plant kingdom, contributing to the diversification of plants. One of the notable features of allopolyploidy is the occurrence of homoeologous exchange (HE) events between the subgenomes, causing changes in genomic composition, gene expression, and phenotypic variations. However, the role of HE in plant adaptation and domestication remains unclear.

RESULTS

Here we analyze the whole-genome resequencing data from Brassica napus accessions representing the different morphotypes and ecotypes, to investigate the role of HE in domestication. Our findings demonstrate frequent occurrence of HEs in Brassica napus, with substantial HE patterns shared across populations, indicating their potential role in promoting crop domestication. HE events are asymmetric, with the A genome more frequently replacing C genome segments. These events show a preference for specific genomic regions and vary among populations. We also identify candidate genes in HE regions specific to certain populations, which likely contribute to flowering-time diversification across diverse morphotypes and ecotypes. In addition, we assemble a new genome of a swede accession, confirming the HE signals on the genome and their potential involvement in root tuber development. By analyzing HE in another allopolyploid species, Brassica juncea, we characterize a potential broader role of HE in allopolyploid crop domestication.

CONCLUSIONS

Our results provide novel insights into the domestication of polyploid Brassica species and highlight homoeologous exchange as a crucial mechanism for generating variations that are selected for crop improvement in polyploid species.

The Application of Paclobutrazol to GA3-Treated Seed Tuber Potato Fields Does Not Shorten the Growth Cycle or Mitigate Tuber Elongation

Potato seed tubers are a valuable product in potato agriculture. Over the years, studies have been conducted to increase the fraction of mid-size tubers, which are used as a planting material, within the general pool of tuber sizes. Gibberellic acid has been a central component of such studies and has successfully increased the seed-size pool. However, in many cases, misshapen tubers were formed, and the practice has not become widespread. The use of the gibberellic acid inhibitor paclobutrazol has been examined for its ability to increase seed tuber number and tuber growth and to overcome the heat inhibition of tuberization in warm climates. Paclobutrazol has been shown to increase tuber yield and growth rate. In this study, we aimed to test whether the combination of gibberellic acid and paclobutrazol can increase the seed tuber pool, reduce the number of misshapen tubers, and shorten the growth cycle, thus avoiding end-of-season elevated heat conditions and reducing agricultural inputs. Our findings suggest that gibberellic acid on its own can lead to an increase in the number of seed tubers at earlier stages of growth; however, the sequential addition of paclobutrazol was not able to drive even earlier growth or lower the number of misshapen tubers.

Tuber, or not tuber: Molecular and morphological basis of underground storage organ development

Underground storage organs occur in phylogenetically diverse plant taxa and arise from multiple tissue types including roots and stems. Thickening growth allows underground storage organs to accommodate carbohydrates and other nutrients and requires proliferation at various lateral meristems followed by cell expansion. The WOX-CLE module regulates thickening growth via the vascular cambium in several eudicot systems, but the molecular mechanisms of proliferation at other lateral meristems are not well understood. In potato, onion, and other systems, members of the phosphatidylethanolamine-binding protein (PEBP) gene family induce underground storage organ development in response to photoperiod cues. While molecular mechanisms of tuber development in potato are well understood, we lack detailed mechanistic knowledge for the extensive morphological and taxonomic diversity of underground storage organs in plants.

Sweet potato yield and quality characteristics affected by different late-season irrigation levels

BACKGROUND

Seasonal late-season water deficits negatively affect the yield and quality of sweet potatoes in northern China. However, the amount of late-season irrigation to achieve high yield and consistent quality storage root remains undetermined. We assessed the yield and some qualitative traits of sweet potatoes such as size, shape, skin/flesh colour and nutritional content, as influenced by five irrigation levels (T0: unirrigated control; T1: 33% ETc; T2: 75% ETc; T3: 100% ETc; and T4: 125% ETc).

RESULTS

Late-season irrigation significantly increased yield and marketable yield. Yields for T2 and T3 were significantly higher than other treatments, whereas T2 had the highest Grade A rating in a 2-year test. The vertical length of storage roots gradually increased with an increase in irrigation level, whereas the maximum width remained unchanged. The proportion of long elliptic and elliptic storage roots also increased, whereas the proportion of ovate, obovate and round storage roots gradually decreased. The skin and flesh colours became more vivid as the level of irrigation increased, with the skin colour becoming redder and the flesh colour becoming more orange-yellow. The levels of carotenoids, vitamin C and soluble sugar were significantly higher in irrigated crops, with the highest vitamin C and soluble sugar levels in T2 and the highest carotenoid levels in T3 treatment.

CONCLUSION

Taken together, these results demonstrate the potential of moderate irrigation in the late-season to improve both yield production and quality potential. The results are of great importance for improving the market value of sweet potatoes and increasing grower profits. © 2024 Society of Chemical Industry.

A Small Auxin-Up RNA Gene, IbSAUR36, Regulates Adventitious Root Development in Transgenic Sweet Potato

Small auxin-upregulated RNAs (SAURs), as the largest family of early auxin-responsive genes, play important roles in plant growth and development processes, such as auxin signaling and transport, hypocotyl development, and tolerance to environmental stresses. However, the functions of few SAUR genes are known in the root development of sweet potatoes. In this study, an IbSAUR36 gene was cloned and functionally analyzed. The IbSAUR36 protein was localized to the nucleus and plasma membrane. The transcriptional level of this gene was significantly higher in the pencil root and leaf.This gene was strongly induced by indole-3-acetic acid (IAA), but it was downregulated under methyl-jasmonate(MeJA) treatment. The promoter of IbSAUR36 contained the core cis-elements for phytohormone responsiveness. Promoter β-glucuronidase (GUS) analysis in Arabidopsis showed that IbSAUR36 is highly expressed in the young tissues of plants, such as young leaves, roots, and buds. IbSAUR36-overexpressing sweet potato roots were obtained by an efficient Agrobacterium rhizogenes-mediated root transgenic system. We demonstrated that overexpression of IbSAUR36 promoted the accumulation of IAA, upregulated the genes encoding IAA synthesis and its signaling pathways, and downregulated the genes encoding lignin synthesis and JA signaling pathways. Taken together, these results show that IbSAUR36 plays an important role in adventitious root (AR) development by regulating IAA signaling, lignin synthesis, and JA signaling pathways in transgenic sweet potatoes.

CPK1-HSP90 phosphorylation and effector XopC2-HSP90 interaction underpin the antagonism during cassava defense-pathogen infection

Cassava is one of the most important tropical crops, but it is seriously affected by cassava bacteria blight (CBB) caused by the bacterial pathogen Xanthomonas phaseoli pv manihotis (Xam). So far, how pathogen Xam infects and how host cassava defends during pathogen-host interaction remains elusive, restricting the prevention and control of CBB. Here, the illustration of HEAT SHOCK PROTEIN 90 kDa (MeHSP90.9) interacting proteins in both cassava and bacterial pathogen revealed the dual roles of MeHSP90.9 in cassava-Xam interaction. On the one hand, calmodulin-domain protein kinase 1 (MeCPK1) directly interacted with MeHSP90.9 to promote its protein phosphorylation at serine 175 residue. The protein phosphorylation of MeHSP90.9 improved the transcriptional activation of MeHSP90.9 clients (SHI-RELATED SEQUENCE 1 (MeSRS1) and MeWRKY20) to the downstream target genes (avrPphB Susceptible 3 (MePBS3) and N-aceylserotonin O-methyltransferase 2 (MeASMT2)) and immune responses. On the other hand, Xanthomonas outer protein C2 (XopC2) physically associated with MeHSP90.9 to inhibit its interaction with MeCPK1 and the corresponding protein phosphorylation by MeCPK1, so as to repress host immune responses and promote bacterial pathogen infection. In summary, these results provide new insights into genetic improvement of cassava disease resistance and extend our understanding of cassava-bacterial pathogen interaction.

TCP transcription factor StAST1 represses potato tuberization by regulating tuberigen complex activity

Potato (Solanum tuberosum L.) is cultivated worldwide for its underground tubers, which provide an important part of human nutrition and serve as a model system for belowground storage organ formation. Similar to flowering, stolon-expressed FLOWERING LOCUS T-like (FT-like) protein SELF-PRUNING 6A (StSP6A) plays an instrumental role in tuberization by binding to the bZIP transcription factors StABI5-like 1 (StABL1) and StFD-like 1 (StFDL1), causing transcriptional reprogramming at the stolon subapical apices. However, the molecular mechanism regulating the widely conserved FT-bZIP interactions remains largely unexplored. Here, we identified a TCP transcription factor StAST1 (StABL1 and StSP6A-associated TCP protein 1) binding to both StSP6A and StABL1. StAST1 is specifically expressed in the vascular tissue of leaves and developing stolons. Silencing of StAST1 leads to accelerated tuberization and a shortened life cycle. Molecular dissection reveals that the interaction of StAST1 with StSP6A and StABL1 attenuates the formation of the alternative tuberigen activation complex (aTAC). We also observed StAST1 directly activates the expression of potato GA 20-oxidase gene (StGA20ox1) to regulate GA responses. These results demonstrate StAST1 functions as a tuberization repressor by regulating plant hormone levels; our findings also suggest a mechanism by which the widely conserved FT-FD genetic module is fine-tuned.

Advances in the Modulation of Potato Tuber Dormancy and Sprouting

The post-harvest phase of potato tuber dormancy and sprouting are essential in determining the economic value. The intricate transition from dormancy to active growth is influenced by multiple factors, including environmental factors, carbohydrate metabolism, and hormonal regulation. Well-established environmental factors such as temperature, humidity, and light play pivotal roles in these processes. However, recent research has expanded our understanding to encompass other novel influences such as magnetic fields, cold plasma treatment, and UV-C irradiation. Hormones like abscisic acid (ABA), gibberellic acid (GA), cytokinins (CK), auxin, and ethylene (ETH) act as crucial messengers, while brassinosteroids (BRs) have emerged as key modulators of potato tuber sprouting. In addition, jasmonates (JAs), strigolactones (SLs), and salicylic acid (SA) also regulate potato dormancy and sprouting. This review article delves into the intricate study of potato dormancy and sprouting, emphasizing the impact of environmental conditions, carbohydrate metabolism, and hormonal regulation. It explores how various environmental factors affect dormancy and sprouting processes. Additionally, it highlights the role of carbohydrates in potato tuber sprouting and the intricate hormonal interplay, particularly the role of BRs. This review underscores the complexity of these interactions and their importance in optimizing potato dormancy and sprouting for agricultural practices.

StCoExpNet: a global co-expression network analysis facilitates identifying genes underlying agronomic traits in potatoes

KEY MESSAGE

We constructed a gene expression atlas and co-expression network for potatoes and identified several novel genes associated with various agronomic traits. This resource will accelerate potato genetics and genomics research. Potato (Solanum tuberosum L.) is the world's most crucial non-cereal food crop and ranks third in food production after wheat and rice. Despite the availability of several potato transcriptome datasets at public databases like NCBI SRA, an effort has yet to be put into developing a global transcriptome atlas and a co-expression network for potatoes. The objectives of our study were to construct a global expression atlas for potatoes using publicly available transcriptome datasets, identify housekeeping and tissue-specific genes, construct a global co-expression network and identify co-expression clusters, investigate the transcriptional complexity of genes involved in various essential biological processes related to agronomic traits, and provide a web server (StCoExpNet) to easily access the newly constructed expression atlas and co-expression network to investigate the expression and co-expression of genes of interest. In this study, we used data from 2299 publicly available potato transcriptome samples obtained from 15 different tissues to construct a global transcriptome atlas. We found that roughly 87% of the annotated genes exhibited detectable expression in at least one sample. Among these, we identified 281 genes with consistent and stable expression levels, indicating their role as housekeeping genes. Conversely, 308 genes exhibited marked tissue-specific expression patterns. We exemplarily linked some co-expression clusters to important agronomic traits of potatoes, such as self-incompatibility, anthocyanin biosynthesis, tuberization, and defense responses against multiple pathogens. The dataset compiled here constitutes a new resource (StCoExpNet), which can be accessed at https://stcoexpnet.julius-kuehn.de . This transcriptome atlas and the co-expression network will accelerate potato genetics and genomics research.

Structure, evolution, and roles of SWEET proteins in growth and stress responses in plants

Carbohydrates are exported by the SWEET family of transporters, which is a novel class of carriers that can transport sugars across cell membranes and facilitate sugar's long-distance transport from source to sink organs in plants. SWEETs play crucial roles in a wide range of physiologically important processes by regulating apoplastic and symplastic sugar concentrations. These processes include host-pathogen interactions, abiotic stress responses, and plant growth and development. In the present review, we (i) describe the structure and organization of SWEETs in the cell membrane, (ii) discuss the roles of SWEETs in sugar loading and unloading processes, (iii) identify the distinct functions of SWEETs in regulating plant growth and development including flower, fruit, and seed development, (iv) shed light on the importance of SWEETs in modulating abiotic stress resistance, and (v) describe the role of SWEET genes during plant-pathogen interaction. Finally, several perspectives regarding future investigations for improving the understanding of sugar-mediated plant defenses are proposed.

Transcriptome Analysis Reveals Novel Genes Potentially Involved in Tuberization in Potato

The formation and development of tubers, the primary edible and economic organ of potatoes, directly affect their yield and quality. The regulatory network and mechanism of tuberization have been preliminarily revealed in recent years, but plenty of relevant genes remain to be discovered. A few candidate genes were provided due to the simplicity of sampling and result analysis of previous transcriptomes related to tuberization. We sequenced and thoroughly analyzed the transcriptomes of thirteen tissues from potato plants at the tuber proliferation phase to provide more reference information and gene resources. Among them, eight tissues were stolons and tubers at different developmental stages, which we focused on. Five critical periods of tuberization were selected to perform an analysis of differentially expressed genes (DEGs), according to the results of the tissue correlation. Compared with the unswollen stolons (Sto), 2751, 4897, 6635, and 9700 DEGs were detected in the slightly swollen stolons (Sto1), swollen stolons (Sto2), tubers of proliferation stage 1 (Tu1), and tubers of proliferation stage 4 (Tu4). A total of 854 transcription factors and 164 hormone pathway genes were identified in the DEGs. Furthermore, three co-expression networks associated with Sto-Sto1, Sto2-Tu1, and tubers of proliferation stages two to five (Tu2-Tu5) were built using the weighted gene co-expression network analysis (WGCNA). Thirty hub genes (HGs) and 30 hub transcription factors (HTFs) were screened and focalized in these networks. We found that five HGs were reported to regulate tuberization, and most of the remaining HGs and HTFs co-expressed with them. The orthologs of these HGs and HTFs were reported to regulate processes (e.g., flowering, cell division, hormone synthesis, metabolism and signal transduction, sucrose transport, and starch synthesis) that were also required for tuberization. Such results further support their potential to control tuberization. Our study provides insights and countless candidate genes of the regulatory network of tuberization, laying the foundation for further elucidating the genetic basis of tuber development.

Research overview on the genetic mechanism underlying the biosynthesis of polysaccharide in tuber plants

Tuber plants are of great significance in the world as human food crops. Polysaccharides, important metabolites in tuber plants, also serve as a source of innovative drugs with significant pharmacological effects. These drugs are particularly known for their immunomodulation and antitumor properties. To fully exploit the potential value of tuber plant polysaccharides and establish a synthetic system for their targeted synthesis, it is crucial to dissect their metabolic processes and genetic regulatory mechanisms. In this article, we provide a comprehensive summary of the basic pathways involved in the synthesis of various types of tuber plant polysaccharides. We also outline the key research progress that has been made in this area in recent years. We classify the main types and functions of tuber plant polysaccharides and analyze the biosynthetic processes and genetic regulation mechanisms of key enzymes involved in the metabolic pathways of starch, cellulose, pectin, and fructan in tuber plants. We have identified hexokinase and glycosyltransferase as the key enzymes involved in the polysaccharide synthesis process. By elucidating the synthesis pathway of polysaccharides in tuber plants and understanding the underlying mechanism of action of key enzymes in the metabolic pathway, we can provide a theoretical framework for enhancing the yield of polysaccharides and other metabolites in plant culture cells. This will ultimately lead to increased production efficiency.

Transcriptional dynamics in source-sink tissues identifies molecular factors regulating the corm development process in saffron (Crocus sativus L.)

AIMS

Geophytic plants have evolved to develop underground storage organs (USO) in the active growing season to withstand harsh environments as well as to coordinate growth and reproduction when conditions are favourable. Saffron is an autumn flowering geophyte and an expensive spice crop restricted to certain geographical locations in the world. Saffron, being sterile, does not produce seeds and thus propagates only through corms, the quality of which determines its yield. Corm development in saffron is unexplored and the underlying molecular mechanism is still elusive. In this study, we performed an extensive characterisation of the transcriptional dynamics in the source (leaf) and sink (corm) tissues during corm development in saffron.

KEY RESULTS

Via morphological and transcriptome studies, we identified molecular factors regulating corm development process in saffron, which defined corm development into three stages: the initiation stage demonstrates enhanced vegetative growth aboveground and swelling of shoot base belowground due to active cell division & carbohydrate storage; the bulking stage comprises of increased source and sink strength, active photosynthesis, circadian gating and starch accumulation; the maturation stage represents reduced source and sink strength, lowered photosynthesis, sugar transport, starch synthesis and cell cycle arrest.

UTILITY

The global view of transcriptional changes in source and sink identifies similar and new molecular factors involved in the saffron corm development process compared to USO formation in other geophytes and provides a valuable resource for dissecting the molecular network underlying the corm development. We propose a hypothetical model based on data analysis, of how molecular factors via environmental cues can regulate the corm development process in saffron.

Different regions and environments have critical roles on yield, main quality and industrialization of an industrial purple-fleshed sweetpotato (Ipomoea batatas L. (Lam.)) "Xuzishu8"

Purple-fleshed sweetpotato (PFSP) (Ipomoea batatas (L.) Lam), whose flesh is purple to dark purple, is a special variety type of sweetpotato, which has the characteristics of food crop, industrial crop and medicinal crop. The storage root (SR) of PFSP is rich in anthocyanins, starch, protein, soluble sugar, mineral elements, polyphenol, dietary fiber and so on, which has balanced and comprehensive nutritional value. And in recent years, its unique nutritional elements are increasingly known for their health functions. At present, there is no article on the characteristics and quality analysis of industrial xz8 variety. To explore the influence of different environments on the processing quality of xz8, we selected nine regions (Xuzhou, Jiawang, Pizhou, Xinyi, Peixian, Sihong, Yanchen, Xiangyang and Tianshui) to measure its yield and quality changes. The data demonstrated that xz8 has a very consistent high yield performance. In Tianshui, the anthocyanins, protein and minerals contents were significantly higher and yield also above average. Moreover, the variety with the lowest starch content exhibited the best taste. On the basis of the above results, it suggested that quite practicable to promote xz8 cultivation and suitable for processing in these areas. Thus, our present findings improve our understanding of xz8 variety and provide the basis for the industrial production of PFSP with strong prospects for success.

Identification of MeC3HDZ1/MeCNA as a potential regulator of cassava storage root development

The storage root (SR) of cassava is the main staple food in sub-Saharan Africa, where it feeds over 500 million people. However, little is known about the genetic and molecular regulation underlying its development. Unraveling such regulation would pave the way for biotechnology approaches aimed at enhancing cassava productivity. Anatomical studies indicate that SR development relies on the massive accumulation of xylem parenchyma, a cell-type derived from the vascular cambium. The C3HDZ family of transcription factors regulate cambial cells proliferation and xylem differentiation in Arabidopsis and other species. We thus aimed at identifying C3HDZ proteins in cassava and determining whether any of them shows preferential activity in the SR cambium and/or xylem. Using phylogeny and synteny studies, we identified eight C3HDZ proteins in cassava, namely MeCH3DZ1-8. We observed that MeC3HDZ1 is the MeC3HDZ gene displaying the highest expression in SR and that, within that organ, the gene also shows high expression in cambium and xylem. In-silico analyses revealed the existence of a number of potential C3HDZ targets displaying significant preferential expression in the SR. Subsequent Y1H analyses proved that MeC3HDZ1 can bind canonical C3HDZ binding sites, present in the promoters of these targets. Transactivation assays demonstrated that MeC3HDZ1 can regulate the expression of genes downstream of promoters harboring such binding sites, thereby demonstrating that MeC3HDZ1 has C3HDZ transcription factor activity. We conclude that MeC3HDZ1 may be a key factor for the regulation of storage root development in cassava, holding thus great promise for future biotechnology applications.

The tuber-specific StbHLH93 gene regulates proplastid-to-amyloplast development during stolon swelling in potato

In potato, stolon swelling is a complex and highly regulated process, and much more work is needed to fully understand the underlying mechanisms. We identified a novel tuber-specific basic helix-loop-helix (bHLH) transcription factor, StbHLH93, based on the high-resolution transcriptome of potato tuber development. StbHLH93 is predominantly expressed in the subapical and perimedullary region of the stolon and developing tubers. Knockdown of StbHLH93 significantly decreased tuber number and size, resulting from suppression of stolon swelling. Furthermore, we found that StbHLH93 directly binds to the plastid protein import system gene TIC56 promoter, activates its expression, and is involved in proplastid-to-amyloplast development during the stolon-to-tuber transition. Knockdown of the target TIC56 gene resulted in similarly problematic amyloplast biogenesis and tuberization. Taken together, StbHLH93 functions in the differentiation of proplastids to regulate stolon swelling. This study highlights the critical role of proplastid-to-amyloplast interconversion during potato tuberization.

Cultivating potential: Harnessing plant stem cells for agricultural crop improvement

Meristems are stem cell-containing structures that produce all plant organs and are therefore important targets for crop improvement. Developmental regulators control the balance and rate of cell divisions within the meristem. Altering these regulators impacts meristem architecture and, as a consequence, plant form. In this review, we discuss genes involved in regulating the shoot apical meristem, inflorescence meristem, axillary meristem, root apical meristem, and vascular cambium in plants. We highlight several examples showing how crop breeders have manipulated developmental regulators to modify meristem growth and alter crop traits such as inflorescence size and branching patterns. Plant transformation techniques are another innovation related to plant meristem research because they make crop genome engineering possible. We discuss recent advances on plant transformation made possible by studying genes controlling meristem development. Finally, we conclude with discussions about how meristem research can contribute to crop improvement in the coming decades.

Traveling with purpose: cell-to-cell transport of plant mRNAs

Messenger RNAs (mRNAs) in multicellular organisms can act as signals transported cell-to-cell and over long distances. In plants, mRNAs traffic cell-to-cell via plasmodesmata (PDs) and over long distances via the phloem vascular system to control diverse biological processes - such as cell fate and tissue patterning - in destination organs. Research on long-distance transport of mRNAs in plants has made remarkable progress, including the cataloguing of many mobile mRNAs, characterization of mRNA features important for transport, identification of mRNA-binding proteins involved in their transport, and understanding of the physiological roles of mRNA transport. However, information on short-range mRNA cell-to-cell transport is still limited. This review discusses the regulatory mechanisms and physiological functions of mRNA transport at the cellular and whole plant levels.

Metabolic GWAS-based dissection of genetic basis underlying nutrient quality variation and domestication of cassava storage root

BACKGROUND

Metabolites play critical roles in regulating nutritional qualities of plants, thereby influencing their consumption and human health. However, the genetic basis underlying the metabolite-based nutrient quality and domestication of root and tuber crops remain largely unknown.

RESULTS

We report a comprehensive study combining metabolic and phenotypic genome-wide association studies to dissect the genetic basis of metabolites in the storage root (SR) of cassava. We quantify 2,980 metabolic features in 299 cultivated cassava accessions. We detect 18,218 significant marker-metabolite associations via metabolic genome-wide association mapping and identify 12 candidate genes responsible for the levels of metabolites that are of potential nutritional importance. Me3GT, MeMYB4, and UGT85K4/UGT85K5, which are involved in flavone, anthocyanin, and cyanogenic glucoside metabolism, respectively, are functionally validated through in vitro enzyme assays and in vivo gene silencing analyses. We identify a cluster of cyanogenic glucoside biosynthesis genes, among which CYP79D1, CYP71E7b, and UGT85K5 are highly co-expressed and their allelic combination contributes to low linamarin content. We find MeMYB4 is responsible for variations in cyanidin 3-O-glucoside and delphinidin 3-O-rutinoside contents, thus controlling SR endothelium color. We find human selection affects quercetin 3-O-glucoside content and SR weight per plant. The candidate gene MeFLS1 is subject to selection during cassava domestication, leading to decreased quercetin 3-O-glucoside content and thus increased SR weight per plant.

CONCLUSIONS

These findings reveal the genetic basis of cassava SR metabolome variation, establish a linkage between metabolites and agronomic traits, and offer useful resources for genetically improving the nutrition of cassava and other root crops.

BEL transcription factors in prominent Solanaceae crops: the missing pieces of the jigsaw in plant development

MAIN CONCLUSION

Understanding BEL transcription factors roles in potato and tomato varies considerably with little overlap. The review suggests reciprocal use of gained results to proceed with the knowledge in both crops The proper development of organs that plants use for reproduction, like fruits or tubers, is crucial for the survival and competitiveness of the species and thus subject to strict regulations. Interestingly, the controls of potato (Solanum tuberosum) tuber and tomato (S. lycopersicum) fruit development use common mechanisms, including the action of the BEL transcription factors (TFs). Although more than ten BEL genes have been identified in either genome, only a few of them have been characterized. The review summarizes knowledge of BEL TFs' roles in these closely related Solanaceae species, focusing on those that are essential for tuberization in potato, namely StBEL5, StBEL11 and StBEL29, and for fruit development in tomato - SlBEL11, SlBL2 and SIBL4. Comprehension of the roles of individual BEL TFs, however, is not yet sufficient. Different levels of understanding of important characteristics are described, such as BEL transcript accumulation patterns, their mobility, BEL protein interaction with KNOX partners, subcellular localisation, and their target genes during initiation and development of the organs in question. A comparison of the knowledge on BEL TFs and their mechanisms of action in potato and tomato may provide inspiration for faster progress in the study of both models through the exchange of information and ideas. Both crops are extremely important for human nutrition. In addition, their production is likely to be threatened by the upcoming climate change, so there is a particular need for breeding using a deep knowledge of control mechanisms.

Agronomic and hormonal approaches for enhancing flowering intensity in white Guinea yam (Dioscorea rotundata Poir.)

Developing novel white Guinea yam (Dioscorea rotundata) varieties is constrained by the sparse, erratic, and irregular flowering behavior of most genotypes. We tested the effectiveness of nine agronomic and hormonal treatments to enhance flowering on D. rotundata under field conditions. Genotypes responded differently to flower-inducing treatments (p<0.001). Of the test treatments, pruning and silver thiosulfate (STS) were effective in increasing the number of spikes per plant and the flowering intensity on both sparse flowering and monoecious cultivars. STS and tuber removal treatments promoted female flowers on the monoecious variety while pruning and most treatments involving pruning favored male flowers. None of the treatments induced flowering on Danacha, a non-flowering yam landrace. Flower-enhancing treatments had no significant effect on flower fertility translated by the fruit set, since most treatments recorded fruit sets above the species' average crossability rate. Flower-enhancing techniques significantly influenced number of tubers per plant (p = 0.024) and tuber dry matter content (DMC, p = 0.0018) but did not significantly affect plant tuber yield. Nevertheless, treatments that could enhance substantially flowering intensity, such as pruning and STS, reduced tuber yield. DMC had negative associations with all flowering-related traits. This study provided insights into white yam flower induction and suggests promising treatments that can be optimized and used routinely to increase flowering in yam crop, without significantly affecting flower fertility and tuber yield.

How metabolism and development are intertwined in space and time

Developmental transitions, occurring throughout the life cycle of plants, require precise regulation of metabolic processes to generate the energy and resources necessary for the committed growth processes. In parallel, the establishment of new cells, tissues, and even organs, alongside their differentiation provoke profound changes in metabolism. It is increasingly being recognized that there is a certain degree of feedback regulation between the components and products of metabolic pathways and developmental regulators. The generation of large-scale metabolomics datasets during developmental transitions, in combination with molecular genetic approaches has helped to further our knowledge on the functional importance of metabolic regulation of development. In this perspective article, we provide insights into studies that elucidate interactions between metabolism and development at the temporal and spatial scales. We additionally discuss how this influences cell growth-related processes. We also highlight how metabolic intermediates function as signaling molecules to direct plant development in response to changing internal and external conditions.

Physiological, anatomical and quality indexes of root tuber formation and development in chayote (Sechium edule)

BACKGROUND

Chayote is an underutilized species of Cucurbitaceae. It is rich in nutrients such as protein, minerals, phenols and its extracts have anti-cardiovascular and anti-cancer effects, making it a versatile plant for both medicinal and culinary purposes. Although research on its root tuber is limited, they are rich in starch and have a structure similar to that of potatoes, cassava, and sweet potatoes. Therefore, they can serve as potential substitutes for potatoes and offer promising prospects as agricultural and industrial resources. However, the physiological and cellular mechanisms of chayote root tuber formation and development are still unclear.

RESULTS

In this study, we observed the growth habit of 'Tuershao' (high yield of root tuber). The results revealed that the tuber enlargement period of 'Tuershao' lasts approximately 120 days, with the early enlargement phase occurring during 0-30 days, rapid enlargement phase during 30-90 days, and maturation phase during 90-120 days. Physiological indicators demonstrated a gradual increase in starch content as the tuber developed. The activities of sucrose synthase (SUS) and invertase (VIN) showed a consistent trend, reaching the highest level in the rapid expansion period, which was the key enzyme affecting tuber expansion. Moreover, the special petal like structure formed by the secondary phloem and secondary xylem of the tuber resulted in its enlargement, facilitating the accumulation of abundant starch within the thin-walled cells of this structure. Principal component analysis further confirmed that starch content, SUS and VIN activities, as well as the concentrations of calcium (Ca), iron (Fe), and selenium (Se), were the major factors influencing tuber development. Moreover, the low temperature environment not only promoted the growth of 'Tuershao' tubers but also enhanced the accumulation of nutritional substances.

CONCLUSIONS

These findings contribute to a deeper understanding of the formation and developmental mechanisms of 'Tuershao' tubers, providing valuable guidance for cultivation practices aimed at improving crop yield.

Effect of blended fertilizer rates and planting density on yield and yield components of Irish potato (Solanum tuberosum L.) at Gombora condition, Hadiya zone, Southern Ethiopia

Potato is an important food and cash crop and it has high yielding potential in many parts of Ethiopia; however the yield of the crop is often constrained due to low and imbalanced rates of inorganic fertilizers and inappropriate spacing. The field experiment was conducted to determine the effect of five rates of blended fertilizer (0, 100, 150, 200, and 250) kg NPS ha^-1 and intra-row planting spacing of 20 cm, 30 cm and 40 cm and laid out by randomized complete block design with three replication in a factorial arrangement. The analysis of variance revealed that, marketable tuber yield, total tuber yield, stem number per hill, total fresh mass, underground fresh and dry mass were significantly (P < 0.05) influenced by the interaction of Nitrogen, Phosphorous and Sulfur (NPS blended fertilizer) and intra-row spacing. The highest plant height (96.60 cm), highest marketable tuber yield (34.29 tha^-1), highest total tuber yield (38.36 t ha^-1) and highest total fresh biomass (1274.2 g plant^-1) were recorded from NPS rate of 250 kg NPS ha^-1 and intra-row spacing of 20 cm while the lowest recorded from control treatment in wider intra-row spacing (40 cm). Therefore, the application of 250 kg NPS ha^-1 with the intra-row spacing of 20 cm can give an optimum tuber yield and it could be recommended for the production of potato in the study area.

Transcriptome profiling reveals the genes involved in tuberous root expansion in Pueraria (Pueraria montana var. thomsonii)

BACKGROUND

Pueraria is a dry root commonly used in Traditional Chinese Medicine or as food and fodder, and tuberous root expansion is an important agronomic characteristic that influences its yield. However, no specific genes regulating tuberous root expansion in Pueraria have been identified. Therefore, we aimed to explore the expansion mechanism of Pueraria at six developmental stages (P1-P6), by profiling the tuberous roots of an annual local variety "Gange No.1" harvested at 105, 135, 165, 195, 225, and 255 days after transplanting.

RESULTS

Observations of the tuberous root phenotype and cell microstructural morphology revealed that the P3 stage was a critical boundary point in the expansion process, which was preceded by a thickening diameter and yield gain rapidly of the tuberous roots, and followed by longitudinal elongation at both ends. A total of 17,441 differentially expressed genes (DEGs) were identified by comparing the P1 stage (unexpanded) against the P2-P6 stages (expanded) using transcriptome sequencing; 386 differential genes were shared across the six developmental stages. KEGG pathway enrichment analysis showed that the DEGs shared by P1 and P2-P6 stages were mainly involved in pathways related to the "cell wall and cell cycle", "plant hormone signal transduction", "sucrose and starch metabolism", and "transcription factor (TF)". The finding is consistent with the physiological data collected on changes in sugar, starch, and hormone contents. In addition, TFs including bHLHs, AP2s, ERFs, MYBs, WRKYs, and bZIPs were involved in cell differentiation, division, and expansion, which may relate to tuberous root expansion. The combination of KEGG and trend analyses revealed six essential candidate genes involved in tuberous root expansion; of them, CDC48, ARF, and EXP genes were significantly upregulated during tuberous root expansion while INV, EXT, and XTH genes were significantly downregulated.

CONCLUSION

Our findings provide new insights into the complex mechanisms of tuberous root expansion in Pueraria and candidate target genes, which can aid in increasing Pueraria yield.

Comparative Transcriptome Analysis Reveals the Effect of Lignin on Storage Roots Formation in Two Sweetpotato (Ipomoea batatas (L.) Lam.) Cultivars

Sweet potato (Ipomoea batatas (L.) Lam.) is one of the most important crops with high storage roots yield. The formation and expansion rate of storage root (SR) plays a crucial role in the production of sweet potato. Lignin affects the SR formation; however, the molecular mechanisms of lignin in SR development have been lacking. To reveal the problem, we performed transcriptome sequencing of SR harvested at 32, 46, and 67 days after planting (DAP) to analyze two sweet potato lines, Jishu25 and Jishu29, in which SR expansion of Jishu29 was early and had a higher yield. A total of 52,137 transcripts and 21,148 unigenes were obtained after corrected with Hiseq2500 sequencing. Through the comparative analysis, 9577 unigenes were found to be differently expressed in the different stages in two cultivars. In addition, phenotypic analysis of two cultivars, combined with analysis of GO, KEGG, and WGCNA showed the regulation of lignin synthesis and related transcription factors play a crucial role in the early expansion of SR. The four key genes swbp1, swpa7, IbERF061, and IbERF109 were proved as potential candidates for regulating lignin synthesis and SR expansion in sweet potato. The data from this study provides new insights into the molecular mechanisms underlying the impact of lignin synthesis on the formation and expansion of SR in sweet potatoes and proposes several candidate genes that may affect sweet potato yield.

Deciphering the hormone regulatory mechanisms of storage root initiation in sweet potato: challenges and future prospects

Sweet potato (Ipomoea batatas) is an economically important food crop that is grown primarily for its edible storage roots. Several researchers have consequently been conducting studies to increase sweet potato yield, and an important aspect of this research involves understanding how storage root initiation occurs. Although significant progress has been made, several challenges associated with studying this crop have resulted in lagging progress compared to other crops and thus sweet potato storage root initiation is not clearly understood. This article highlights the most important aspects of the hormone signalling processes during storage root initiation that needs to be investigated further and suggests candidate genes that should be prioritized for further study, based on their importance in storage organ formation in other crops. Lastly, ways of overcoming the challenges associated with studying this crop are suggested.

New Horizons in Plant Photoperiodism

Photoperiod-measuring mechanisms allow organisms to anticipate seasonal changes to align reproduction and growth with appropriate times of the year. This review provides historical and modern context to studies of plant photoperiodism. We describe how studies of photoperiodic flowering in plants led to the first theoretical models of photoperiod-measuring mechanisms in any organism. We discuss how more recent molecular genetic studies in Arabidopsis and rice have revisited these concepts. We then discuss how photoperiod transcriptomics provides new lessons about photoperiodic gene regulatory networks and the discovery of noncanonical photoperiod-measuring systems housed in metabolic networks of plants. This leads to an examination of nonflowering developmental processes controlled by photoperiod, including metabolism and growth. Finally, we highlight the importance of understanding photoperiodism in the context of climate change, delving into the rapid latitudinal migration of plant species and the potential role of photoperiod-measuring systems in generating photic barriers during migration.

Long-distance control of potato storage organ formation by SELF PRUNING 3D and FLOWERING LOCUS T-like 1

Plants program their meristem-associated developmental switches for timely adaptation to a changing environment. Potato (Solanum tuberosum L.) tubers differentiate from specialized belowground branches or stolons through radial expansion of their terminal ends. During this process, the stolon apex and closest axillary buds enter a dormancy state that leads to tuber eyes, which are reactivated the following spring and generate a clonally identical plant. The potato FLOWERING LOCUS T homolog SELF-PRUNING 6A (StSP6A) was previously identified as the major tuber-inducing signal that integrates day-length cues to control the storage switch. However, whether some other long-range signals also act as tuber organogenesis stimuli remains unknown. Here, we show that the florigen SELF PRUNING 3D (StSP3D) and FLOWERING LOCUS T-like 1 (StFTL1) genes are activated by short days, analogously to StSP6A. Overexpression of StSP3D or StFTL1 promotes tuber formation under non-inductive long days, and the tuber-inducing activity of these proteins is graft transmissible. Using the non-tuber-bearing wild species Solanum etuberosum, a natural SP6A null mutant, we show that leaf-expressed SP6A is dispensable for StSP3D long-range activity. StSP3D and StFTL1 mediate secondary activation of StSP6A in stolon tips, leading to amplification of this tuberigen signal. StSP3D and StFTL1 were observed to bind the same protein partners as StSP6A, suggesting that they can also form transcriptionally active complexes. Together, our findings show that additional mobile tuber-inducing signals are regulated by the photoperiodic pathway.

Photosynthesis Product Allocation and Yield in Sweet Potato in Response to Different Late-Season Irrigation Levels

Soil water deficit is an important factor affecting the source-sink balance of sweet potato during its late-season growth, but water regulation during this period has not been well studied. Therefore, the aim of this study was to determine the appropriate irrigation level in late-season sweet potato, and the effect of irrigation level on accumulation and allocation of photosynthetic products. In this study, two yield-based field trials (2021-2022) were conducted in which five late-season irrigation levels set according to the crop evapotranspiration rate were tested (T₀: non-irrigation, T₁: 33% ET_c, T₂: 75% ET_c, T₃: 100% ET_c, T₄: 125% ET_c). The effects of the different irrigation levels on photosynthetic physiological indexes, ¹³C transfer allocation, water use efficiency (WUE), water productivity (WP), and the yield and economic benefit of sweet potato were studied. The results showed that late-season irrigation significantly increased the total chlorophyll content and net photosynthetic rate of functional leaves, in addition to promoting the accumulation of above-ground-source organic biomass (p < 0.05). The rate of ¹³C allocation, maximum accumulation rate (V_max), and average accumulation rate (V_mean) of dry matter in storage root were significantly higher under T₂ irrigation than under the other treatments (p < 0.05). This suggests that both non-irrigation (T₀) and over-irrigation (T₄) were not conducive to the transfer and allocation of photosynthetic products to storage roots in late-season sweet potato. However, moderate irrigation (T₂) effectively promoted the source-sink balance, enhanced the source photosynthetic rate and stimulated the sink activity, such that more photosynthate was allocated to the storage sink. The results also showed that T₂ irrigation treatments significantly increased yield, WUE and WP compared to T₀ and T₄ (p < 0.05), suggesting that moderate irrigation (T₂) can significantly promote the potential of storage root production and field productivity. There was a close relationship between economic benefit and marketable sweet potato yield, and both were highest under T₂ (p < 0.05), increasing by 36.1% and 59.9% compared with T₀ over the two-year study period. In conclusion, irrigation of late-season sweet potato with 75% evapotranspiration (T₂) can improve both the yield and production potential. Together, these results support the use of late-season water management in the production of sweet potato.