Rice最新文献

Grain size is vital determinant for grain yield and quality, which specified by its three-dimensional structure of seeds (length, width and thickness). The ZINC FINGER-HOMEODOMAIN (ZHD) proteins play critical roles in plant growth and development. However, the information regarding the function in reproductive development of ZHD proteins is scarce. Here, we deeply characterized the phenotype of oszhd1, oszhd2, and oszhd1oszhd2. The single mutants of OsZHD1/2 were similar with wild type. Nevertheless, the double mutant displayed dwarfism and smaller reproductive organs, and shorter, narrower, and thinner grain size. oszhd1oszhd2 revealed a significant decrease in total cell length and number, and single cell width in outer parenchyma; reducing the average width of longitudinal epidermal cells, but the length were increased in outer and inner glumes of oszhd1oszhd2 compared with wild-type, oszhd1-1, oszhd2-1, respectively. OsZHD1 and OsZHD2 encoded the nucleus protein and were distributed predominately in stem and the developing spikelets, asserting their roles in grain size. Meanwhile, yeast two-hybrid, bimolecular fluorescence complementation, and Co-immunoprecipitation assay clarified that OsZHD1 could directly interacted with OsZHD2. The differential expression analysis showed that 839 DEGs, which were down-regulated in oszhd1oszhd2 than wild type and single mutants, were mainly enriched in secondary metabolite biosynthetic, integral component of membrane, and transporter activity pathway. Moreover, it is reliable that the altered expression of cell cycle and expansion-related and grain size-related genes were observed in RNA-seq data, highly consistent with the qRT-PCR results. Altogether, our results suggest that OsZHD1/2 are functional redundancy and involved in regulating grain size by influencing cell proliferation in rice.

Polyploid plants exhibit strong resistance to salt and cadmium (Cd) stress, which can adversely affect their growth, reducing crop quality and yield. Transcriptome analysis, antioxidant enzymatic activities, physiological measurements of reactive oxygen species, and heterosis analysis were performed on hybrids with neo-tetraploid rice and its progenitors. The results showed that diploid hybrids had fluctuating yields in early and late seasons, while tetraploid hybrids had consistent grain yield throughout. Transcriptome analysis revealed that gene expression related to sugar metabolism processes increased in tetraploid hybrids. Transcriptome analysis revealed several genes associated with heterosis and stress, including OsEAF6, which is associated with heterosis, and OsCIPK14, which is involved in defense signalling pathways. Furthermore, compared to the parents, hybrids have a much higher number of genes associated with abiotic stress. Consequently, diploid and tetraploid hybrids were treated with Cd (0 and 100 µM) and NaCl (200 mM) in the present study. Under Cd toxicity, the levels of carotenoids were reduced by 33.31% and 45.59%, while the levels of chlorophyll a declined by 16.00% and 27.81% in tetraploid and diploid hybrids, respectively, compared to the control. Tetraploid hybrids had the highest germination rate under salt stress and the lowest Cd uptake compared to diploid hybrids and their parents. In general, the activities of antioxidant enzymes exhibited a considerable drop, whereas the levels of H₂O₂ and MDA showed a remarkable increase in parents compared to hybrids. Under cadmium toxicity, the expression of OsERF1 in tetraploid rice was increased, and OsABCC1 and OsHMA3 were highly expressed in neo-tetraploid rice. Interspecific hybrid (indica and japonica) displayed enhanced tolerance to cadmium and salinity stress, potentially serving as a natural resource to improve rice resilience. These findings provide a basis for understanding polyploid rice's gene expression pattern, environmental tolerance, and heterosis.

In rice, internode elongation is a critical aspect of plant development and agricultural productivity. Previous morphological and histochemical studies using [³H]thymidine have visualized the cell division zone (intercalary meristem) in internodes. However, it has remained unclear how the intercalary meristem forms during stem development. In addition, while a pith cavity forms in the central part of the rice stem, the spatiotemporal relationship between pith cavity formation and intercalary meristem development is not well understood. Therefore, we performed histological analysis of intercalary meristem and pith cavity development using C9285, a deepwater rice variety that shows internode elongation from the vegetative growth stage. We classified the developmental stages of the stem into four stages based on the analysis of pith cavity formation using Trypan blue, Calcein-AM, and MitoRed staining, and visualized dividing cells using the Click-iT EdU imaging assay. In Stage 1, no pith cavity was formed. Vertical cell rows were observed between above the axillary bud attachment and the upper node, suggesting anticlinal divisions that lead to internode formation in the early stage of stem development. In Stage 2, the first pith cavity formed in the pith of the foot, which is the region of axillary bud attachment. Compared to cell division in the internode, that in the foot was significantly activated resulting in slight elongation from Stage 1 to Stage 2. In Stage 3, cell division in the foot ceased, while active cell division at the base of the internode led to significant vertical elongation. The second pith cavity formed due to cell death in the pith of the internode. In Stage 4, the two pith cavities connected to form a single large pith cavity. Although the intercalary meristem maintained cell division activity, the number of cell divisions decreased. Based on these results, we propose a model for stem development that involves two phases of elongation regulation: primary elongation involving slight elongation in the foot, and secondary elongation involving significant internode elongation due to the activation of cell division and cell elongation in the intercalary meristem. This is the first study to anatomically elucidate the spatiotemporal relationship between intercalary meristem development and pith cavity formation in rice stem development. It provides new insights for future research on rice stem development and studies of other grass species.

Molecular farming for producing biopharmaceuticals in plants is considered an excellent method to replace some of the production methods currently used, and a significant number of recombinant proteins have already shown the potential to facilitate this. In particular, production of activin A, which has a variety of important biological functions in humans, is limited. The purpose of this study was to develop a safe, stable, and efficient plant-based in vitro production system for activin A, assess its biological activity in cancer cells, and demonstrate its potential for use in cancer research. We evaluated the expression and production of activin A in plant cells through a mass culture and secretion system. The formation of mature activin A homodimers, produced by enterokinase, was also assessed. Southern blot and inverse PCR were performed to investigate the gene insertion sites in the plants, and the stability of activin A was evaluated over six months under various pH conditions. The activity of plant-derived activin A was analyzed in HEK293T, Huh7, MCF7, and MDA-MB-231 cancer cell lines using luciferase reporter, migration, phosphorylation, and gelatin zymography assays. We developed cell line #71, which showed the highest levels of mature activin A expression (8.44 μg/g calli fresh weight) and had multicopy gene insertions. Pro-activin A was converted to mature activin A using enterokinase. We demonstrated that the optimal stability of plant-derived activin A was maintained for six months at pH 7 below 4 °C. Plant-derived activin A significantly enhanced activin A signaling activity in HEK293T, Huh7, and MCF7 cancer cells. Additionally, we confirmed that plant-derived activin A inhibited the growth of Huh7 cancer cells by activating the Smad pathway without affecting the MAPK pathway. Contrastingly, in MDA-MB-231 breast cancer cells, plant-derived activin A promoted cell migration. Our results confirm that plant-derived activin A, produced using a mass production system, exhibits full biological activity and affects cancer cell behavior in a manner similar to activin A derived from traditional mammalian systems. Furthermore, this study highlights the importance of considering cellular context when determining the functional outcomes of activin A treatment.

Wild rice, as the ancestor of cultivated rice, has accumulated a wide range of beneficial traits through prolonged natural selection and evolution. Oryza officinalis, belonging to the CC genome, differs significantly from the AA genome. In this study, we utilized second- and third-generation sequencing, along with Hi-C technology, to assemble the genome of MT10 (O. officinalis). The assembled genome is 552.58 Mb, with contigs and scaffold N50 values of 40.04 and 44.48 Mb, respectively, and 96.73% of the sequences anchored to 12 chromosomes. A total of 33,813 genes were annotated, and repetitive sequences account for 54.24% of the MT10 genome. The number of unique genes in MT10 exceeds that in the O. officinalis genome from Thailand, and their divergence time is estimated at 1.6 million years ago. The MT10 genome exhibits fewer expanded gene families compared to contracted ones, with the expanded families predominantly associated with disease and pest resistance. Comparative genomic analysis of MT10 and Nipponbare reveals sequence variations in biotic and abiotic resistance-related genes. In particular, the presence of R genes and cystatin gene families in MT10 may contribute to its unique insect resistance. Transcriptome analyses indicate that flavonoid biosynthesis and MAPK-related genes are expressed in response to brown planthopper infestation. This study represents the first chromosome-level genome assembly of MT10, providing a reference sequence for the efficient cloning of beneficial genes from O. officinalis, which holds significant potential for the genetic improvement of cultivated rice.

Chloroplasts are vital for photosynthesis, and their development necessitates proper expression of chloroplast genes. However, the regulatory mechanisms underlying rice chloroplast gene expression have not been fully elucidated. In this study, we obtained an albino mutant of rice, white seedling and lethal 1 (wsl1), which displays significantly decreased chlorophyll contents and impaired chloroplast ultrastructure. The causal gene Oryza sativa PEP-RELATED DEVELOPMENT ARRESTED 1 (OsPRDA1) was isolated using Mutmap + and verified by gene editing and complementary assays. The expression of OsPRDA1 is induced by light, and OsPRDA1 is localized in chloroplasts. Transcription sequencing revealed that genes related to photosynthesis were differentially expressed in wsl1. The expression levels of the examined plastid-encoded RNA polymerase (PEP)-dependent chloroplast genes are downregulated due to the mutation of OsPRDA1. Moreover, OsPRDA1 interacts with OsFSD2, a member of PEP-associated proteins (PAPs). Knockout of OsFSD2 leads to the albino and seedling-lethal phenotype and downregulation of PEP-dependent chloroplast genes. Together, our results demonstrated that OsPRDA1 plays essential roles in rice chloroplast development, probably by facilitating the function of the PAP complex and chloroplast gene expression.

High temperature significantly impacts grain appearance quality, yet few studies have focused on identifying new quantitative trait loci (QTLs)/genes related to these traits under heat stress during the flowering stage in rice. In this study, a natural population of 525 rice accessions was used to identify QTLs and candidate genes associated with grain appearance quality using a Genome-Wide Association Study under heat stress. We identified 25 QTLs associated with grain length (GL), grain width (GW), and grain chalkiness (GC) under heat stress across 10 chromosomes in the three rice populations (full, indica, and japonica). Notably, three sets of overlapping QTLs were identified (set 1: qHTT-L3 and qHTT-XL3; set 2: qHTT-C5 and qHTT-XC5; set 3: qHTT-L11.1 and qHTT-GL11), located on chromosomes 3, 5, and 11, respectively. Haplotype analysis indicated that Hap1 is the superior haplotype, and pyramiding more than two superior alleles improved rice grain appearance quality (longer GL, wider GW, and lower GC) in high-temperature environments. Based on RNA-seq, qRT-PCR and functional annotations analysis, LOC_Os05g06920, LOC_Os05g06970, and LOC_Os11g28104 were highly expressed, identifying them as the high-priority candidate genes for QTLs linked to grain appearance quality (GL, GW, and GC) under heat stress. Expression analysis revealed that LOC_Os05g06920, which encodes a relA-SpoT-like protein RSH4, and LOC_Os11g28104, which encodes a protein kinase with a DUF26 domain, were highly expressed in seeds, leaves, and shoots. And LOC_Os05g06970, encoding a peroxidase precursor, exhibited high expression levels in roots. Compared to the wild-type (WT) plants, the mutants of LOC_Os05g06920, LOC_Os05g06970, and LOC_Os11g28104 exhibited increased GL and grain length-to-width ratio, but reduced GW under both natural and heat stress conditions, while the LOC_Os05g06970 and LOC_Os11g28104 mutants significantly increased the chalky grain rate and grain chalkiness degree under natural conditions. Furthermore, the LOC_Os05g06920, LOC_Os05g06970, and LOC_Os11g28104 mutants showed a lower decline in grain appearance quality traits than the WT after high-temperature treatment. These findings suggest that LOC_Os05g06920, LOC_Os05g06970, and LOC_Os11g28104 play crucial roles in regulating both grain development and heat tolerance under heat stress at anthesis, thus affecting grain appearance quality in rice. Our results provide a promising genetic resource for improving rice grain appearance quality under heat stress.

Salinity is a major abiotic stress that adversely affects rice growth and production. However, the detailed regulatory mechanisms of salt stress response in rice remain largely unexplored. In this study, we established that the RING-type E3 ubiquitin ligase OsRFI2 plays a negative role in salt tolerance in rice. Knockout mutants of OsRFI2 (Osrfi2) exhibited high tolerance, whereas OsRFI2-overexpressed transgenic lines (OE-OsRFI2) were more sensitive to salt stress. OsRFI2 that has E3 ligase activity interacts with ascorbate peroxidase OsAPX8 in chloroplast, and catalyzes its ubiquitination and degradation through the 26 S proteasome pathway. The Osapx8 mutants, like OE-OsRFI2 lines, showed high sensitivity to high salt concentrations, accumulating greater amounts of MDA, H₂O₂ and O₂^-, which lead to compromised cell permeability and ROS accumulation. Thus, the OsRFI2-OsAPX8 module adds novel clues for better understanding the regulatory mechanism of salt stress response in rice.

Nitrate can directly activate phosphate (Pi) starvation signaling, ultimately promoting plant growth by enhancing phosphorus absorption and utilization and optimizing the balance of nitrogen and phosphorus nutrients. However, the complex mechanisms by which plants integrate complex nutrient signals from nitrogen to phosphorus are not well understood. This study highlights the importance of Calcineurin B-like protein-1 (OsCBL1), a calcium sensor, in coordinating nitrogen and phosphorus signaling in rice. Knockdown of OsCBL1 in rice reduced the expression of genes involved in nitrate-induced Pi starvation responses. In high nitrate conditions, OsCBL1-KD plants displayed diminished biomass gain, unlike the wild-type rice, which thrived under elevated phosphate levels. In OsCBL1-KD plants, OsSPX4, a key repressor in nitrogen and phosphorus signaling, remains undegraded in the presence of nitrate due to the significantly reduced expression of OsNRT1.1B. Moreover, the OsCBL1 knockdown hampers the movement of the nitrogen-related transcription factor, OsNLP4, from the cytoplasm to the nucleus when nitrate is present. This impedes the expression of OsNRT1.1B, as OsNLP4 can directly bind to the promoter of OsNRT1.1B nitrate responsive cis-element (NRE) and activate its expression. In summary, these findings suggest that OsCBL1 plays a pivotal role in regulating OsNRT1.1B expression by managing the transport of OsNLP4 between cytoplasm and nucleus in response to nitrate availability. This regulation subsequently influences the phosphate response triggered by nitrate and optimizes the coordinated utilization of nitrogen and phosphorus.