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Salt stress is an environmental factor that limits plant growth and crop production. With the rapid expansion of salinized arable land worldwide, investigating the molecular mechanisms underlying the salt stress response in plants is urgently needed. Here, we report that GROWTH REGULATING FACTOR 7 (OsGRF7) promotes salt tolerance by regulating arbutin (hydroquinone-β-D-glucopyranoside) metabolism in rice (Oryza sativa). Overexpression of OsGRF7 increased arbutin content, and exogenous arbutin application rescued the salt-sensitive phenotype of OsGRF7 knockdown and knockout plants. OsGRF7 directly promoted the expression of the arbutin biosynthesis genes URIDINE DIPHOSPHATE GLYCOSYLTRANSFERASE 1 (OsUGT1) and OsUGT5, and knockout of OsUGT1 or OsUGT5 reduced rice arbutin content, salt tolerance, and grain size. Furthermore, OsGRF7 degradation through its interaction with F-BOX AND OTHER DOMAINS CONTAINING PROTEIN 13 reduced rice salinity tolerance and grain size. These findings highlight an underexplored role of OsGRF7 in modulating rice arbutin metabolism, salt stress response, and grain size, as well as its broad potential use in rice breeding. Transcription factor control of arbutin biosynthesis gene expression regulates grain size and salt stress response in rice (Oryza sativa). [ABSTRACT FROM AUTHOR]

Summary: Marker‐based prediction holds great promise for improving current plant and animal breeding efficiencies. However, the predictabilities of complex traits are always severely affected by negative factors, including distant relatedness, environmental discrepancies, unknown population structures, and indeterminate numbers of predictive variables. In this study, we utilised two independent F1 hybrid populations in the years 2012 and 2015 to predict rice thousand grain weight (TGW) using parental untargeted metabolite profiles with a partial least squares regression method. A stable predictive model for TGW was built based on hybrids from the population in 2012 (r = 0.75) but failed to properly predict TGW for hybrids from the population in 2015 (r = 0.27). After integrating hybrids from both populations into the training set, the TGW of hybrids could be predicted but was largely dependent on population structures. Then, core hybrids from each population were determined by principal component analysis and the TGW of hybrids in both environments were successfully predicted (r > 0.60). Moreover, adjusting the population structures and numbers of predictive analytes increased TGW predictability for hybrids in 2015 (r = 0.72). Our study demonstrates that the TGW of F1 hybrids across environments can be accurately predicted based on parental untargeted metabolite profiles with a core hybridisation strategy in rice. Metabolic biomarkers identified from early developmental stage tissues, which are grown under experimental conditions, may represent a workable approach towards the robust prediction of major agronomic traits for climate‐adaptive varieties. [ABSTRACT FROM AUTHOR]

The restoration fertility complex ( RFC) was previously identified in Honglian ( HL)-cytoplasmic male sterility ( CMS) rice ( Oryza sativa), and glycine-rich protein 162 ( GRP162) is responsible for binding to the CMS-associated transcript atp6-orfH79., Here, we engineered a recombinant GRP162 containing the mitochondrial transit peptide, termed Mt- GRP162, as an artificial restorer of fertility ( Rf) gene. Mt- GRP162 was confirmed to bind to CMS-associated RNA and to localize to the mitochondria. The transgenic plants showed restored fertility with partially functional pollen., We found that the expression of ORFH79 decreased in transgenic plants, while the expression of atp6-orfH79 was not changed. These findings indicate that Mt- GRP162 restores fertility by suppressing the expression of the cytotoxic protein ORFH79 at the post-transcriptional level rather than via the cleavage of atp6-orfH79 in the presence of RFC., These findings contribute to our understanding of the mechanisms of restoration through diverse pathways. [ABSTRACT FROM AUTHOR]

Cytoplasmic male sterility ( CMS) has attracted great interest because of its application in crop breeding. Despite increasing knowledge of CMS, not much is understood about its molecular mechanisms. Previously, orf H79 was cloned and identified as the CMS gene in Honglian rice, but how the ORFH79 protein causes pollen abortion is still unknown., Through bacterial two-hybrid library screening, P61, a subunit of the mitochondrial electron transport chain ( ETC) complex III, was selected as a candidate that interacts with ORFH79. Bimolecular fluorescence complementation ( Bi FC) and coimmunoprecipitation (co IP) assays verified their interaction inside mitochondria. Blue native polyacrylamide gel electrophoresis ( BN- PAGE) and western blotting showed ORF79 and P61 colocalized in mitochondrial ETC complex III of CMS lines., Compared with the maintainer line, Yuetai B ( YB), a significant decrease of enzyme activity was detected in mitochondrial complex III of the CMS line, Yuetai A ( YA), which resulted in decreased ATP concentrations and an increase in the reactive oxygen species ( ROS) content., We propose that the CMS protein, ORFH79, can bind to complex III and decrease its enzyme activity through interaction with P61. This defect results in energy production dysfunction and oxidative stress in mitochondria, which may work as retrograde signals that lead to abnormal pollen development. [ABSTRACT FROM AUTHOR]