A bamboo leaf-specific aquaporin gene PePIP2;7 is involved in abiotic stress response

Advances in bamboo genomics: Growth and development, stress tolerance, and genetic engineering

Bamboo is a fast-growing and ecologically significant plant with immense economic value due to its applications in construction, textiles, and bioenergy. However, research on bamboo has been hindered by its long vegetative period, unpredictable flowering cycles, and challenges in genetic transformation. Recent developments in advanced sequencing and genetic engineering technologies have provided new insights into bamboo's evolutionary history, developmental biology, and stress resilience, paving the way for improved conservation and sustainable utilization. This review synthesizes the latest findings on bamboo's genomics, biotechnology, and the molecular mechanisms governing its growth, development, and stress response. Key genes and regulatory pathways controlling its rapid growth, internode elongation, rhizome development, culm lignification, flowering, and abiotic stress responses have been identified through multi-omics and functional studies. Complex interactions among transcription factors, epigenetic regulators, and functionally important genes shape bamboo's unique growth characteristics. Moreover, progress in genetic engineering techniques, including clustered regularly interspaced short palindromic repeats-based genome editing, has opened new avenues for targeted genetic improvements. However, technical challenges, particularly the complexity of polyploid bamboo genomes and inefficient regeneration systems, remain significant barriers to functional studies and large-scale breeding efforts. By integrating recent genomic discoveries with advancements in biotechnology, this review proposes potential strategies to overcome existing technological limitations and to accelerate the development of improved bamboo varieties. Continued efforts in multi-omics research, gene-editing applications, and sustainable cultivation practices will be essential for harnessing bamboo as a resilient and renewable resource for the future. The review presented here not only deepens our understanding of bamboo's genetic architecture but also provides a foundation for future research aimed at optimizing its ecological and industrial potential.

Physiological and transcriptomic analysis of the effect of overexpression of the NTPIP2;4 gene on drought tolerance in tobacco

Aquaporins are widely present in the plant kingdom and play important roles in plant response to abiotic adversity stresses such as water and temperature extremes. In this study, we investigated the regulatory role of NTPIP2;4 on drought tolerance in tobacco at physiological and transcriptional levels. In this experiment, we constructed an NtPIP2;4 overexpression vector and genetically transformed tobacco variety 'K326' to investigate the mechanism of NtPIP2;4 gene in regulating drought tolerance in tobacco at physiological and transcriptomic levels. Physiological analyses showed that overexpression plants showed low wilting under drought conditions compared to wild-type (WT), and NtPIP2;4 overexpression tobacco plants showed enhanced superoxide dismutase (SOD) and catalase (CAT) activities, lower levels of superoxide anion (O2-), malondialdehyde (MDA), and hydrogen peroxide (H2O2) than the control, and significantly higher proline (Pro) content than the control. The leaves of NtPIP2;4 overexpressing plants and wild-type controls after drought were subjected to transcriptome sequencing, and RNA-seq analysis showed that a total of 1752 differentially expressed genes (DEGs) were obtained under drought conditions, with 1005 DEGs of up-regulated and 747 DEGs of down-regulated differentially expressed genes. The DEGs were enriched mainly in the plant MAPK signaling pathway, the plant hormone signal transduction pathway, amino sugar and nucleotide sugar metabolism, starch and sucrose metabolism and plant-pathogen interaction pathways. We also investigated the drought pathway of MAPK pathway and the auxin pathway mechanism of plant hormone signal transduction pathway, and found that the transcript levels of the genes of the relevant pathways changed, and hypothesized that NtPIP2;4 might regulate the drought resistance of plants through the expression of the relevant genes induced by auxin. This study demonstrates that overexpression of NtPIP2;4 gene can enhance the drought resistance of tobacco plants, which will provide a basis for the research on the function of tobacco NtPIP2;4 gene and the creation of new germplasm resources.

A bamboo 'PeSAPK4-PeMYB99-PeTIP4-3' regulatory model involved in water transport

Water plays crucial roles in expeditious growth and osmotic stress of bamboo. Nevertheless, the molecular mechanism of water transport remains unclear. In this study, an aquaporin gene, PeTIP4-3, was identified through a joint analysis of root pressure and transcriptomic data in moso bamboo (Phyllostachys edulis). PeTIP4-3 was highly expressed in shoots, especially in the vascular bundle sheath cells. Overexpression of PeTIP4-3 could increase drought and salt tolerance in transgenic yeast and rice. A co-expression pattern of PeSAPK4, PeMYB99 and PeTIP4-3 was revealed by WGCNA. PeMYB99 exhibited an ability to independently bind to and activate PeTIP4-3, which augmented tolerance to drought and salt stress. PeSAPK4 could interact with and phosphorylate PeMYB99 in vivo and in vitro, wherein they synergistically accelerated PeTIP4-3 transcription. Overexpression of PeMYB99 and PeSAPK4 also conferred drought and salt tolerance in transgenic rice. Further ABA treatment analysis indicated that PeSAPK4 enhanced water transport in response to stress via ABA signaling. Collectively, an ABA-mediated cascade of PeSAPK4-PeMYB99-PeTIP4-3 is proposed, which governs water transport in moso bamboo.

De novo transcriptomic analysis of Doum Palm (Hyphaene compressa) revealed an insight into its potential drought tolerance

BACKGROUND

Doum palms (Hyphaene compressa) perform a crucial starring role in the lives of Kenya's arid and semi-arid people for empowerment and sustenance. Despite the crop's potential for economic gain, there is a lack of genetic resources and detailed information about its domestication at the molecular level. Given the doum palm's vast potential as a widely distributed plant in semi-arid and arid climates and a source of many applications, coupled with the current changing climate scenario, it is essential to understand the molecular processes that provide drought resistance to this plant.

RESULTS

Assembly of the first transcriptome of doum palms subjected to water stress generated about 39.97 Gb of RNA-Seq data. The assembled transcriptome revealed 193,167 unigenes with an average length of 1655 bp, with 128,708 (66.63%) successfully annotated in seven public databases. Unigenes exhibited significant differentially expressed genes (DEGs) in well-watered and stressed-treated plants, with 45071 and 42457 accounting for up-regulated and down-regulated DEGs, respectively. GO term, KEGG, and KOG analysis showed that DEGs were functionally enriched cellular processes, metabolic processes, cellular and catalytic activity, metabolism, genetic information processing, signal transduction mechanisms, and posttranslational modification pathways. Transcription factors (TF), such as the MYB, WRKY, NAC family, FAR1, B3, bHLH, and bZIP, were the prominent TF families identified as doum palm DEGs encoding drought stress tolerance.

CONCLUSIONS

This study provides a complete understanding of DEGs involved in drought stress at the transcriptome level in doum palms. This research is, therefore, the foundation for the characterization of potential genes, leading to a clear understanding of its drought stress responses and providing resources for improved genetic modification.

Genome-Wide Identification and Gene Expression Analysis of Sweet Cherry Aquaporins (Prunus avium L.) under Abiotic Stresses

Aquaporins (AQPs) are integral transmembrane proteins well known as channels involved in the mobilization of water, small uncharged molecules and gases. In this work, the main objective was to carry out a comprehensive study of AQP encoding genes in Prunus avium (cv. Mazzard F12/1) on a genome-wide scale and describe their transcriptional behaviors in organs and in response to different abiotic stresses. A total of 28 non-redundant AQP genes were identified in Prunus spp. Genomes, which were phylogenetically grouped into five subfamilies (seven PIPs, eight NIPs, eight TIPs, three SIPs and two XIPs). Bioinformatic analyses revealed a high synteny and remarkable conservation of structural features among orthologs of different Prunus genomes. Several cis-acting regulatory elements (CREs) related to stress regulation were detected (ARE, WRE3, WUN, STRE, LTR, MBS, DRE, AT-rich and TC-rich). The above could be accounting for the expression variations associated with plant organs and, especially, each abiotic stress analyzed. Gene expressions of different PruavAQPs were shown to be preferentially associated with different stresses. PruavXIP2;1 and PruavXIP1;1 were up-regulated in roots at 6 h and 72 h of hypoxia, and in PruavXIP2;1 a slight induction of expression was also detected in leaves. Drought treatment strongly down-regulated PruavTIP4;1 but only in roots. Salt stress exhibited little or no variation in roots, except for PruavNIP4;1 and PruavNIP7;1, which showed remarkable gene repression and induction, respectively. Interestingly, PruavNIP4;1, the AQP most expressed in cherry roots subjected to cold temperatures, also showed this pattern in roots under high salinity. Similarly, PruavNIP4;2 consistently was up-regulated at 72 h of heat and drought treatments. From our evidence is possible to propose candidate genes for the development of molecular markers for selection processes in breeding programs for rootstocks and/or varieties of cherry.

PhePLATZ1, a PLATZ transcription factor in moso bamboo (Phyllostachys edulis), improves drought resistance of transgenic Arabidopsis thaliana

Drought is one of the most serious environmental stresses. Plant AT-rich sequence and zinc-binding (PLATZ) proteins perform indispensable functions to regulate plant growth and development and to respond to environmental stress. In this present study, we identified PhePLATZ1 in moso bamboo and found that its expression was up-regulated in response to 20% PEG-6000 and abscisic acid (ABA) treatments. Next, transgenic PhePLATZ1-overexpressing Arabidopsis lines were generated. Overexpression of PhePLATZ1 improved drought stress resistance of transgenic plants by mediating osmotic regulation, enhancing water retention capacity and reducing membrane and oxidative damage. These findings were corroborated by analysing physiological indicators including chlorophyll, relative water content, leaf water loss rate, electrolyte leakage, H₂O₂, proline, malondialdehyde content and the enzyme activities of peroxidase and catalase. Subsequent seed germination and seedling root length experiments that included exposure to exogenous ABA treatments showed that ABA sensitivity decreased in transgenic plants relative to wild-type plants. Moreover, transgenic PhePLATZ1-overexpressing plants promoted stomatal closure in response to ABA treatment, suggesting that PhePLATZ1 might play a positive regulatory role in the drought resistance of plants via the ABA signaling pathway. In addition, the transgenic PhePLATZ1-OE plants showed altered expression of some stress-related genes when grown under drought conditions. Taken together, these findings improve our understanding of the drought response of moso bamboo and provide a key candidate gene for the molecular breeding of this species for drought tolerance.

Pearl Millet Aquaporin Gene PgPIP2;6 Improves Abiotic Stress Tolerance in Transgenic Tobacco

Pearl millet [Pennisetum glaucum (L) R. Br.] is an important cereal crop of the semiarid tropics, which can withstand prolonged drought and heat stress. Considering an active involvement of the aquaporin (AQP) genes in water transport and desiccation tolerance besides several basic functions, their potential role in abiotic stress tolerance was systematically characterized and functionally validated. A total of 34 AQP genes from P. glaucum were identified and categorized into four subfamilies, viz., plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin-26-like intrinsic proteins (NIPs), and small basic intrinsic proteins (SIPs). Sequence analysis revealed that PgAQPs have conserved characters of AQP genes with a closer relationship to sorghum. The PgAQPs were expressed differentially under high vapor pressure deficit (VPD) and progressive drought stresses where the PgPIP2;6 gene showed significant expression under high VPD and drought stress. Transgenic tobacco plants were developed by heterologous expression of the PgPIP2;6 gene and functionally characterized under different abiotic stresses to further unravel their role. Transgenic tobacco plants in the T2 generations displayed restricted transpiration and low root exudation rates in low- and high-VPD conditions. Under progressive drought stress, wild-type (WT) plants showed a quick or faster decline of soil moisture than transgenics. While under heat stress, PgPIP2;6 transgenics showed better adaptation to heat (40°C) with high canopy temperature depression (CTD) and low transpiration; under low-temperature stress, they displayed lower transpiration than their non-transgenic counterparts. Cumulatively, lower transpiration rate (Tr), low root exudation rate, declined transpiration, elevated CTD, and lower transpiration indicate that PgPIP2;6 plays a role under abiotic stress tolerance. Since the PgPIP2;6 transgenic plants exhibited better adaptation against major abiotic stresses such as drought, high VPD, heat, and cold stresses by virtue of enhanced transpiration efficiency, it has the potential to engineer abiotic stress tolerance for sustained growth and productivity of crops.

Identification and Expression Analyses of Invertase Genes in Moso Bamboo Reveal Their Potential Drought Stress Functions

Invertases (INVs) can irreversibly hydrolyze sucrose into fructose and glucose, which play principal roles in carbon metabolism and responses to various stresses in plants. However, little is known about the INV family in bamboos, especially their potential function in drought stress. In this study, 29 PeINVs were identified in moso bamboo (Phyllostachys edulis). They were clustered into alkaline/neutral invertase (NINV) and acid invertase (AINV) groups based on the gene structures, conserved motifs, and phylogenetic analysis results. The collinearity analysis showed nine segmental duplication pairs within PeINVs, and 25 pairs were detected between PeINVs and OsINVs. PeINVs may have undergone strong purification selection during evolution, and a variety of stress and phytohormone-related regulatory elements were found in the promoters of PeINVs. The tissue-specific expression analysis showed that PeINVs were differentially expressed in various moso bamboo tissues, which suggested that they showed functional diversity. Both the RNA-seq and quantitative real-time PCR results indicated that four PeINVs were significantly upregulated under drought stress. Co-expression network and Pearson’s correlation coefficient analyses showed that these PeINVs co-expressed positively with sugar and water transport genes (SWTGs), and the changes were consistent with sugar content. Overall, we speculate that the identified PeINVs are spatiotemporally expressed, which enables them to participate in moso bamboo growth and development. Furthermore, PeINVs, together with SWTGs, also seem to play vital roles in the response to drought stress. These results provide a comprehensive information resource for PeINVs, which will facilitate further study of the molecular mechanism underlying PeINVs involvement in the response to drought stress in moso bamboo.

Two Aquaporin Genes, GhPIP2;7 and GhTIP2;1, Positively Regulate the Tolerance of Upland Cotton to Salt and Osmotic Stresses

Aquaporins (AQPs) facilitate the transport of water and small molecules across intrinsic membranes and play a critical role in abiotic stresses. In this study, 111, 54, and 56 candidate AQP genes were identified in Gossypium hirsutum (AD₁), Gossypium arboreum (A₂), and Gossypium raimondii (D₅), respectively, and were further classified into five subfamilies, namely, plasma intrinsic protein (PIP), tonoplast intrinsic protein (TIP), nodulin 26-like intrinsic protein (NIP), small basic intrinsic protein (SIP), and uncategorized X intrinsic protein (XIP). Transcriptome analysis and quantitative real-time PCR (qRT-PCR) revealed some high-expression GhPIPs and GhTIPs (PIP and TIP genes in G. hirsutum, respectively) in drought and salt stresses. GhPIP2;7-silenced plants decreased in the chlorophyll content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity comparing the mock control (empty-vector) under 400 mM NaCl treatment, which indicated a positive regulatory role of GhPIP2;7 in salt tolerance of cotton. The GhTIP2;1-silenced cotton plants were more sensitive to osmotic stress. GhTIP2;1-overexpressed plants exhibited less accumulation of H₂O₂ and malondialdehyde but higher proline content under osmotic stress. In summary, our study elucidates the positive regulatory roles of two GhAQPs (GhPIP2;7 and GhTIP2;1) in salt and osmotic stress responses, respectively, and provides a new gene resource for future research.