Grain number and size are interactive agronomic traits that determine grain yield. However, the molecular mechanisms responsible for coordinating the trade-off between these traits remain elusive. Here, we characterized the rice () () mutant, which has larger grains but sparser panicles than the wild type due to disordered localized cell differentiation and proliferation. encodes the mitogen-activated protein kinase phosphatase OsMKP1, a dual-specificity phosphatase of unknown function. Reduced expression of resulted in larger and fewer grains, whereas increased expression resulted in more grains but reduced grain size. GSN1 directly interacts with and inactivates the mitogen-activated protein kinase OsMPK6 via dephosphorylation. Consistent with this finding, the suppression of mitogen-activated protein kinase genes ,, and separately resulted in denser panicles and smaller grains, which rescued the mutant phenotypes. Therefore, OsMKKK10-OsMKK4-OsMPK6 participates in panicle morphogenesis and acts on a common pathway in rice. We confirmed that GSN1 is a negative regulator of the OsMKKK10-OsMKK4-OsMPK6 cascade that determines panicle architecture. The GSN1-MAPK module coordinates the trade-off between grain number and grain size by integrating localized cell differentiation and proliferation. These findings provide important insights into the developmental plasticity of the panicle and a potential means to improve crop yields.
As sessile organisms, plants have evolved numerous strategies to acclimate to changes in environmental temperature. However, the molecular basis of this acclimation remains largely unclear. In this study we identified a tRNA His guanylyltransferase, AET1, which contributes to the modification of pre-tRNA His and is required for normal growth under high-temperature conditions in rice. Interestingly, AET1 possibly interacts with both RACK1A and eIF3h in the endoplasmic reticulum. Notably, AET1 can directly bind to OsARF mRNAs including the uORFs of OsARF19 and OsARF23, indicating that AET1 is associated with translation regulation. Furthermore, polysome profiling assays suggest that the translational status remains unaffected in the aet1 mutant, but that the translational efficiency of OsARF19 and OsARF23 is reduced; moreover, OsARF23 protein levels are obviously decreased in the aet1 mutant under high temperature, implying that AET1 regulates auxin signaling in response to high temperature. Our findings provide new insights into the molecular mechanisms whereby AET1 regulates the environmental temperature response in rice by playing a dual role in tRNA modification and translational control.
Auxin is a crucial phytohormone, controlling multiple aspects of plant growth and responses to the changing environment. However, the role of local auxin biosynthesis in specific developmental programs remains unknown in crops. This study characterized the rice tillering and small grain 1 (tsg1) mutant, which has more tillers but a smaller panicle and grain size resulting from a reduction in endogenous auxin. TSG1 encodes a tryptophan aminotransferase that is allelic to the FISH BONE (FIB) gene. The tsg1 mutant showed hypersensitivity to indole-3-acetic acid and the competitive inhibitor of aminotransferase, L-kynurenine. TSG1 knockout resulted in an increased tiller number but reduction in grain number and size, and decrease in height. Meanwhile, deletion of the TSG1 homologs OsTAR1, OsTARL1, and OsTARL2 caused no obvious changes, although the phenotype of the TSG1/OsTAR1 double mutant was intensified and infertile, suggesting gene redundancy in the rice tryptophan aminotransferase family. Interestingly, TSG1 and OsTAR1, but not OsTARL1 and OsTARL2, displayed marked aminotransferase activity. Meanwhile, subcellular localization was identified as the endoplasmic reticulum, while phylogenetic analysis revealed functional divergence of TSG1 and OsTAR1 from OsTARL1 and OsTARL2. These findings suggest that TSG1 dominates the tryptophan aminotransferase family, playing a prominent role in local auxin biosynthesis in rice.
Grain weight is one of the major factors determining single plant yield production of rice and other cereal crops. Research has begun to reveal the regulatory mechanisms underlying grain weight as well as grain size, highlighting the importance of this research for plant molecular biology. The developmental trait of grain weight is affected by multiple molecular and genetic aspects that lead to dynamic changes in cell division, expansion and differentiation. Additionally, several important biological pathways contribute to grain weight, such as ubiquitination, phytohormones, G-proteins, photosynthesis, epigenetic modifications and microRNAs. Our review integrates early and more recent findings, and provides future perspectives for how a more complete understanding of grain weight can optimize strategies for improving yield production. It is surprising that the acquired wealth of knowledge has not revealed more insights into the underlying molecular mechanisms. To accelerating molecular breeding of rice and other cereals is becoming an emergent and critical task for agronomists. Lastly, we highlighted the importance of leveraging gene editing technologies as well as structural studies for future rice breeding applications.
Background Leaf morphology and spikelet number are two important traits associated with grain yield. To understand how genes coordinating with sink and sources of cereal crops is important for grain yield improvement guidance. Although many researches focus on leaf morphology or grain number in rice, the regulating molecular mechanisms are still unclear. Results In this study, we identified a prohibitin complex 2α subunit, NAL8, that contributes to multiple developmental process and is required for normal leaf width and spikelet number at the reproductive stage in rice. These results were consistent with the ubiquitous expression pattern of NAL8 gene. We used genetic complementation, CRISPR/Cas9 gene editing system, RNAi gene silenced system and overexpressing system to generate transgenic plants for confirming the fuctions of NAL8. Mutation of NAL8 causes a reduction in the number of plastoglobules and shrunken thylakoids in chloroplasts, resulting in reduced cell division. In addition, the auxin levels in nal8 mutants are higher than in TQ, while the cytokinin levels are lower than in TQ. Moreover, RNA-sequencing and proteomics analysis shows that NAL8 is involved in multiple hormone signaling pathways as well as photosynthesis in chloroplasts and respiration in mitochondria. Conclusions Our findings provide new insights into the way that NAL8 functions as a molecular chaperone in regulating plant leaf morphology and spikelet number through its effects on mitochondria and chloroplasts associated with cell division.
18Background 19 In recent years, the plant morphology has been well studied by multiple approaches at 20 cellular and subcellular levels. Two-dimensional (2D) microscopy techniques offer 21 imaging of plant structures on a wide range of magnifications for researchers. However, 22 subcellular imaging is still challenging in plant tissues like roots and seeds. 23 Results 24Here we use a three-dimensional (3D) imaging technology based on the ZEISS X-ray 25 microscope (XRM) Versa and analyze several plant tissues from different plant species. 26 The XRM provides new insights into plant structures using non-destructive imaging at 27 high-resolution and high contrast. We also developed a workflow aiming to acquire 28 accurate and high-quality images in the context of the whole specimen. Multiple plant 29 samples including rice, tobacco, Arabidopsis and maize were used to display the 30 differences of phenotypes, which indicates that the XRM is a powerful tool to 31 investigate plant microstructure. 32 Conclusions 33 Our work provides a novel observation method to evaluate and quantify tissue specific 34 differences for a range of plant species. This new tool is suitable for non-destructive 35 seed observation and screening. 36 37 Keywords: X-ray microscopy, plant morphology, plant development, plant 3D 38 reconstruction 39 Background 40 Since the invention and development of microscopes, it has extended human vision 41 substantially. The observation of cellular and subcellular structures using microscopes 42 have broadened our knowledge to understand the biological world more efficiently [1]. 43 ZEISS and many other microscopy manufacturing companies are spending an 44 enormous amount of time and resources developing higher resolution microscopy 45 systems to assist scientists acquire more detailed images in their research fields. From 46 the single cell organism blue-green algae (Cyanobacteria) to over a hundred-meter-tall 47 giant tree (Eucalyptus regnans), plants display versatile morphologies to survive in 48 different environments. Therefore, utilizing microscopy techniques to study the cellular 49 and subcellular and physiological traits is essential in plant research.50 51 In the 21 st century, microscopy companies provide a variety of measurement techniques 52 for scientists. With the assistance of electron microscopy, plant scientists can observe 53 the cell surface and the detailed structure of organelles, and even decipher the structure 54 of proteins [2-4]. Optical microscopes, including upright and inverted microscopes, 55 provide powerful solutions for cellular observations as well [5, 6]. Since the application 56 of green fluorescent protein, confocal microscopy and various fluorescence related 57 techniques advanced the biological research field [7]. Furthermore, the methods to 58 analyze the corresponding data have been developed at a similar pace [8]. For larger 59 sample observation, stereoscopic microscopy offers non-destructive and detailed 60 insights to identify the tiny differences in betw...
Hybrid sterility is the major obstacle to the utilization of inter-subspecific heterosis in hybrid rice breeding. The S5 locus, composed of three adjacent genes ORF3, ORF4, and ORF5, plays a crucial role in regulating indica/japonica hybrids’ female sterility. Through a series of crosses involving 38 parents, three alleles of S5, ORF3+ORF4−ORF5n, ORF3+ORF4+ORF5n, and ORF3−/ORF4−/ORF5n, all could be regarded as wide-compatibility alleles, and when crossed with indica or japonica rice, they all showed significantly high fertility. Then, in order to explore the genes’ function, we further knocked out genes by using CRISPR/Cas9-based genome editing. Our results demonstrate that the ORF3+ was not just the protector in the killer-protector system, and knocking out ORF3 of the indica allele seriously affected the rice’s normal development. We observed the concrete enhancing hybrid spikelet fertility from the crosses between the ORF4+ knockout japonica materials with indica varieties. By conducting the comparative RNA-Seq analysis of young spikelets, we found that the ORF4+/ORF4− could modulate the hybrid fertility by affecting the expressions of genes related to the function of the Golgi apparatus. This study indicated that knocking out the ORF4+ of the japonica allele or using the alleles carrying ORF5n would provide effective approaches to overcome indica/japonica hybrid female sterility in rice breeding.
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