Search

Background Rice productivity is adversely affected by environmental stresses. Transcription factors (TFs), as the regulators of gene expression, are the key players contributing to stress tolerance and crop yield. Histone gene binding protein-1b (OsHBP1b) is a TF localized within the Saltol QTL in rice. Recently, we have reported the characterization of OsHBP1b in relation to salinity and drought tolerance in a model system tobacco. In the present study, we over-express the full-length gene encoding OsHBP1b in the homologous system (rice) to assess its contribution towards multiple stress tolerance and grain yield. Results We provide evidence to show that transgenic rice plants over-expressing OsHBP1b exhibit better survival and favourable osmotic parameters under salinity stress than the wild type counterparts. These transgenic plants restricted reactive oxygen species accumulation by exhibiting high antioxidant enzyme activity (ascorbate peroxidase and superoxide dismutase), under salinity conditions. Additionally, these transgenic plants maintained the chlorophyll concentration, organellar structure, photosynthesis and expression of photosynthesis and stress-related genes even when subjected to salinity stress. Experiments conducted for other abiotic stresses such as drought and high temperature revealed improved tolerance in these transgenic plants with better root and shoot growth, better photosynthetic parameters, and enhanced antioxidant enzyme activity, in comparison with WT. Further, the roots of transgenic lines showed large cortical cells and accumulated a good amount of callose, unlike the WT roots, thus enabling them to penetrate hard soil and prevent the entry of harmful ions in the cell. Conclusion Collectively, our results show that rice HBP1b gene contributes to multiple abiotic stress tolerance through several molecular and physiological pathways and hence, may serve as an important gene for providing multiple stress tolerance and improving crop yield in rice. Electronic supplementary material The online version of this article (10.1186/s12284-019-0316-8) contains supplementary material, which is available to authorized users.

Background To delineate the adaptive mechanisms operative under salinity stress, it is essential to study plant responses at the very early stages of stress which are very crucial for governing plant survival and adaptation. We believe that it is the initial perception and response phase which sets the foundation for stress adaptation in rice seedlings where plants can be considered to be in a state of osmotic shock and ion buildup. Results An isobaric Tags for Relative and Absolute Quantitation (iTRAQ) approach was used to analyze the pre-existing differences as well as the very early salt shock responsive changes in the proteome of seedlings of contrasting rice genotypes, viz salt-sensitive IR64 and salt-tolerant Pokkali. In response to a quick salt shock, shoots of IR64 exhibited hyperaccumulation of Na+, whereas in Pokkali, these ions accumulated more in roots. Interestingly, we could find 86 proteins to be differentially expressed in shoots of Pokkali seedlings under non-stress conditions whereas under stress, 63 proteins were differentially expressed in Pokkali shoots in comparison to IR64. However, only, 40 proteins under non-stress and eight proteins under stress were differentially expressed in Pokkali roots. A higher abundance of proteins involved in photosynthesis (such as, oxygen evolving enhancer proteins OEE1 & OEE3, PsbP) and stress tolerance (such as, ascorbate peroxidase, superoxide dismutase, peptidyl-prolyl cis-trans isomerases and glyoxalase II), was observed in shoots of Pokkali in comparison to IR64. In response to salinity, selected proteins such as, ribulose bisphosphate carboxylase/oxygenase activase, remained elevated in Pokkali shoots. Glutamate dehydrogenase - an enzyme which serves as an important link between Krebs cycle and metabolism of amino acids was found to be highly induced in Pokkali in response to stress. Similarly, other enzymes such as peroxidases and triose phosphate isomerase (TPI) were also altered in roots in response to stress. Conclusion We conclude that Pokkali rice seedlings are primed to face stress conditions where the proteins otherwise induced under stress in IR64, are naturally expressed in high abundance. Through specific alterations in its proteome, this proactive stress machinery contributes towards the observed salinity tolerance in this wild rice germplasm. Electronic supplementary material The online version of this article (10.1186/s12284-018-0259-5) contains supplementary material, which is available to authorized users.

Background The Na+/Ca2+ Exchanger (NCX) protein family is a member of the Cation/Ca2+ exchanger superfamily and its members play important roles in cellular Ca2+ homeostasis. While the functions of NCX family of proteins is well understood in humans, not much is known about the total complement of Na+/Ca2+ exchangers in plants and their role in various physiological and developmental processes. In the present study, we have identified all the NCX proteins encoded in the genomes of rice and Arabidopsis and studied their phylogeny, domain architecture and expression profiles across different tissues, at various developmental stages and under stress conditions. Results Through whole genome investigation, we identified twenty-two NCX proteins encoded by fifteen genes in rice and sixteen NCX proteins encoded by thirteen genes in Arabidopsis. Based on phylogenetic reconstruction, these could be classified into five clades, members of most of which were found to possess distinct domain architecture. Expression profiling of the identified NCX genes using publicly available MPSS and microarray data showed differential expression patterns under abiotic stresses, and at various development stages. In rice, OsNCX1, OsNCX8, OsNCX9 and OsNCX15 were found to be highly expressed in all the plant parts and various developmental stages. qRT-PCR based expression analysis revealed that OsNCX3, OsNCX10 and OsNCX15 were highly induced by salt and dehydration stress. Besides, expression profiling showed differential regulation of rice NCX genes in response to calcium and EGTA. Interestingly, expression of none of the NCX genes was found to be co-regulated by NaCl and calcium. Conclusions Together, our results present insights into the potential role of NCX family of proteins in abiotic stresses and development. Findings of the present investigation should serve as a starting point for future studies aiming functional characterization of plant NCX family proteins.

Background Crop improvement targeting high yield and tolerance to environmental stresses has become the need of the hour. Yield improvement via breeding or gene pyramiding aiming comprehensive incorporation of the agronomically favored traits requires an in-depth understanding of the molecular basis of these traits. The present study describes expression profiling of yield-related genes in rice with respect to different developmental stages and various abiotic stress conditions. Results Our analysis indicates developmental regulation of the yield-related genes pertaining to the genetic reprogramming involved at the corresponding developmental stage. The gene expression data can be utilized to specifically select particular genes which can potentially function synergistically for enhancing the yield while maintaining the source-sink balance. Furthermore, to gain some insights into the molecular basis of yield penalty during various abiotic stresses, the expression of selected yield-related genes has also been analyzed by qRT-PCR under such stress conditions. Our analysis clearly showed a tight transcriptional regulation of a few of these yield-related genes by abiotic stresses. The stress-responsive expression patterns of these genes could explain some of the most important stress-related physiological manifestations such as reduced tillering, smaller panicles and early completion of the life cycle owing to reduced duration of vegetative and reproductive phases. Conclusions Development of high yielding rice varieties which maintain their yield even under stress conditions may be achieved by simultaneous genetic manipulation of certain combination of genes such as LRK1 and LOG, based on their function and expression profile obtained in the present study. Our study would aid in investigating in future, whether over-expressing or knocking down such yield-related genes can improve the grain yield potential in rice.