Altered regulation of flowering expands growth ranges and maximizes yields in major crops

Sensitivity to Photoperiod Is a Complex Trait in Camelina sativa

Day neutrality, or insensitivity to photoperiod (day length), is an important domestication trait in many crop species. Although the oilseed crop C. sativa has been cultivated since the Neolithic era, day-neutral accessions have yet to be described. We sought to leverage genetic diversity in existing germplasms to identify C. sativa accessions with low photoperiod sensitivity for future engineering of this trait. To do so, we quantified variation in hypocotyl length across 161 C. sativa accessions of 4-day-old seedlings grown in long-day and short-day conditions as a high-throughput approximation of variation in the photoperiod response. Soil-grown adult plants from selected accessions also showed variation in the response to day length in several traits; however, the responses in seedling and adult traits were not correlated, suggesting complex mechanistic underpinnings. Although RNA-seq experiments of the reference accession Licalla identified several differentially regulated Arabidopsis syntelogs involved in photoperiod response and development, including COL2, FT, LHY, and WOX4, expression of these genes in the accessions did not correlate with differences in their photoperiod sensitivity. Taken together, we show that all tested accessions show some degree of photoperiod response and that this trait is likely complex, involving several and separable seedling and adult traits.

The Role of FT/TFL1 Clades and Their Hormonal Interactions to Modulate Plant Architecture and Flowering Time in Perennial Crops

Human nutrition is inherently associated with the cultivation of vegetables, grains, and fruits, underscoring the critical need to understand and manipulate the balance between vegetative and reproductive development in plants. Despite the vast diversity within the plant kingdom, these developmental processes share conserved and interconnected pathways among angiosperms, predominantly involving age, vernalization, gibberellin, temperature, photoperiod, and autonomous pathways. These pathways interact with environmental cues and orchestrate the transition from vegetative growth to reproductive stages. Related to this, there are two key genes belonging to the same Phosphatidylethanolamine-binding proteins family (PEBP), the FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1), which activate and repress the floral initiation, respectively, in different plant species. They compete for transcription factors such as FLOWERING LOCUS D (FD) and 14-3-3 to form floral activation complexes (FAC) and floral repression complexes (FRC). The FT/TFL1 mechanism plays a pivotal role in meristem differentiation, determining developmental outcomes as determinate or indeterminate. This review aims to explore the roles of FT and TFL1 in plant architecture and floral induction of annual and perennial species, together with their interactions with plant hormones. In this context, we propose that plant development can be modulated by the response of FT and/or TFL1 to plant growth regulators (PGRs), which emerge as potential tools for mitigating the adverse effects of environmental changes on plant reproductive processes. Thus, understanding these mechanisms is crucial to address the challenges of agricultural practices, especially in the face of climate change.

Unveiling Drought Tolerant Cotton Genotypes: Insights from Morpho-Physiological and Biochemical Markers at Flowering

Drought stress substantially restricts cotton growth, decreasing cotton production potential worldwide. This study evaluated cotton genotypes at the flowering stage to identify drought-resilient genotypes under moderate and severe drought conditions using physio-morphic and biochemical markers. Five genotypes were examined in a completely randomized design with three replicates across three treatments. Growth and biochemical traits were measured after 14 days of drought stress. The Multi-trait Genotype-Ideotype Distance Index (MGIDI) identified the most drought-tolerant genotypes. Severe drought had a pronounced negative effect on growth and biochemical traits, followed by moderate drought. Among the genotypes, FH-912 exhibited the strongest resilience, with significant increases in proline, peroxidase, catalase, and total chlorophyll. In contrast, chlorophyll a and transpiration rates were largely unaffected. Genotypes VH-351, VH-281, and GH-99 showed moderate drought tolerance, while FH-556 was highly sensitive to water stress. Statistical analyses, including ANOVA, PCA, and heatmaps, confirmed FH-912's superior performance under drought stress. The drought-resilient genotype, FH-912, holds promise for breeding drought-tolerant cotton varieties to sustain cotton productivity in water-limited environments, especially in drought-prone regions.

Overexpression of the general transcription factor OsTFIIB5 alters rice development and seed quality

KEY MESSAGE

Overexpression of general transcription factor OsTFIIB5 in rice affects seedling growth, plant height, flowering time, panicle architecture, and seed protein/starch levels and involves modulation of expression of associated genes. TFIIB, a key general transcription factor (GTF), plays a critical role in pre-initiation complex (PIC) formation and facilitates RNA polymerase II-mediated transcription. In humans and yeast, TFIIB is encoded by a single gene; however, in plants it is encoded by a multigene family whose products may perform specialized transcriptional functions. The role of plant TFIIBs, particularly in monocots, remains largely unexplored. This study presents the first functional characterization of the rice TFIIB gene, OsTFIIB5 (LOC_Os09g36440), during development. Expression profiling of OsTFIIB5 revealed differential patterns across various developmental stages, with pronounced transcript accumulation during seed development. Overexpression of OsTFIIB5 impacted multiple stages of plant growth and development, leading to phenotypic changes such as altered seedling growth, reduced plant height, early heading, altered panicle architecture, decreased yield, and changes in seed storage substances. Notably, there were no effects on seed germination, pollen development, and grain size. Reduction in shoot length and plant height was linked to altered expression of genes involved in gibberellin (GA) biosynthesis, signalling, and deactivation. Overexpression of OsTFIIB5 enhanced the expression of genes involved in the photoperiodic flowering pathway, resulting in early panicle emergence. Higher expression levels of OsTFIIB5 also induced the accumulation of seed storage proteins (SSPs), while reducing starch content and altering the proportions of amylose and amylopectin in seeds. These findings suggest that OsTFIIB5 functions as a transcriptional regulator, governing multiple aspects of rice growth and development.

Phosphorus-Mediated Transition from Vegetative to Reproductive Growth in Dwarf Coconut (Cocos nucifera L.)

Reducing the time before the flowering stage in coconut (Cocos nucifera L.) trees greatly influences yield, yet the mechanisms driving the switch from vegetative to reproductive growth are not well understood, especially the role of phosphorus in this transition. In this study, dwarf coconut plants of the same cultivation age were selected and categorized into the vegetative phase (VP) or the reproductive phase (RP). By examining the phenotypic traits, nutrient variations in the roots and soil, and the transcriptional expression of relevant genes in the roots across both phases, we investigated the potential mechanisms driving the transition from the VP to the RP in coconuts. The shoots of coconuts in the RP were significantly taller compared to those in the VP. Moreover, the phosphorus concentration in the roots of coconuts during the RP was 1.31 times higher than in the VP, which may be linked to the significant upregulation of the PT1 genes AZ11G0219160 and AZ02G0034860 in the roots of coconuts in the RP. In addition, all phosphorus-containing metabolites in the roots during the RP showed a significant increase, particularly those related to long-chain fatty acids and ribonucleotide metabolites. This suggests that coconut roots may facilitate the progression from vegetative to reproductive growth by enhancing phosphorus uptake via PT1s and promoting the synthesis and accumulation of phosphorus-containing metabolites.

Artificial selection of two antagonistic E3 ubiquitin ligases finetunes soybean photoperiod adaptation and grain yield

The precise control of flowering time is of utmost importance for crop adaptation to varying environmental conditions and consequently determines grain yield and plant fitness. Soybean E2, the homolog of Arabidopsis GIGANTEA, is a major locus contributing to high-latitude adaptation and is involved in photoperiod sensitivity. However, due to major effects of E2, additional genetic loci controlling soybean flowering and adaptation have historically been masked and difficult to identify. Here, by eliminating the effect of E2, we identified a Tof9 locus controlling flowering in which ZEITLUPE 2 (ZTL2) is the causal gene. ZTL2 encodes an F-box E3 ubiquitin ligase with homology to Arabidopsis ZEITLUPE and is shown to play a key role in the soybean photoperiodic flowering pathway. ZTL2 physically interacts with E2 to mediate its degradation. Intriguingly, ZTL2 and FKF1, both belong to the F-box-type E3 ubiquitin-ligase family, exhibit opposite roles in regulating soybean flowering. ZTL2 degrades E2, leading to early flowering, while FKF1 stabilizes E2, resulting in delayed flowering. The balance between ZTL2-mediated degradation and FKF1-mediated stabilization enables soybeans to finetune flowering time and maximize grain yield. Field-grown ztl2 mutants are taller, flower late, and have increased yield parameters. ZTL2 and FKF1b bear contrasting artificial-selection patterns to adapt to different latitudes. This antagonistic regulation is crucial for soybean adaptation to diverse ecological settings and allows plants to fine-tune their flowering time in response to photoperiod and latitudinal changes.

Refining flowering date enhances sesame yield independently of day-length

BACKGROUND

The transition from vegetative to reproductive growth is a key factor in yield maximization. Sesame (Sesamum indicum), an indeterminate short-day oilseed crop, is rapidly being introduced into new cultivation areas. Thus, decoding its flowering mechanism is necessary to facilitate adaptation to environmental conditions. In the current study, we uncover the effect of day-length on flowering and yield components using F2 populations segregating for previously identified quantitative trait loci (Si_DTF QTL) confirming these traits.

RESULTS

Generally, day-length affected all phenotypic traits, with short-day preceding days to flowering and reducing yield components. Interestingly, the average days to flowering required for yield maximization was 50 to 55 days, regardless of day-length. In addition, we found that Si_DTF QTL is more associated with seed-yield and yield components than with days to flowering. A bulk-segregation analysis was applied to identify additional QTL differing in allele frequencies between early and late flowering under both day-length conditions. Candidate genes mining within the identified major QTL intervals revealed two flowering-related genes with different expression levels between the parental lines, indicating their contribution to sesame flowering regulation.

CONCLUSIONS

Our findings demonstrate the essential role of flowering date on yield components and will serve as a basis for future sesame breeding.

WRKY22 Transcription Factor from Iris laevigata Regulates Flowering Time and Resistance to Salt and Drought

Iris laevigata Fisch. is an excellent ornamental plant in cold regions due to its unique ornamental ability and strong cold resistance. However, the flowering period of the population is only about 20 days, greatly limiting its potential uses in landscaping and the cutting flower industry. In addition, I. laevigata is often challenged with various abiotic stresses including high salinity and drought in its native habitats. Thus, breeding novel cultivars with delayed flowering time and higher resistance to abiotic stress is of high importance. In this study, we utilized sequencing data from the I. laevigata transcriptome to identify WRKYs and characterized IlWRKY22, a key transcription factor that modulates flowering time and abiotic stress responses. IlWRKY22 is induced by salt and drought stress. We cloned IlWRKY22 and found that it is a Group IIe WRKY localized in the nucleus. Overexpressing IlWRKY22 in Arabidopsis thaliana (L.) Heynh. and Nicotiana tabacum L. resulted in a delayed flowering time in the transgenic plants. We created transgenic N. tabacum overexpressing IlWRKY22, which showed significantly improved resistance to both salt and drought compared to the control plants. Thus, our study revealed a unique dual function of IlWRKY22, an excellent candidate gene for breeding novel Iris cultivars of desirable traits.

Origin, variation, and selection of natural alleles controlling flowering and adaptation in wild and cultivated soybean

Soybean (Glycine max) is an economically important crop worldwide, serving as a major source of oil and protein for human consumption and animal feed. Cultivated soybean was domesticated from wild soybean (Glycine soja) which both species are highly sensitive to photoperiod and can grow over a wide geographical range. The extensive ecological adaptation of wild and cultivated soybean has been facilitated by a series of genes represented as quantitative trait loci (QTLs) that control photoperiodic flowering and maturation. Here, we review the molecular and genetic basis underlying the regulation of photoperiodic flowering in soybean. Soybean has experienced both natural and artificial selection during adaptation to different latitudes, resulting in differential molecular and evolutionary mechanisms between wild and cultivated soybean. The in-depth study of natural and artificial selection for the photoperiodic adaptability of wild and cultivated soybean provides an important theoretical and practical basis for enhancing soybean adaptability and yield via molecular breeding. In addition, we discuss the possible origin of wild soybean, current challenges, and future research directions in this important topic.