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Premature leaf senescence affects plant growth and yield in rice. NAD plays critical roles in cellular redox reactions and remains at a sufficient level in the cell to prevent cell death. Although numerous factors affecting leaf senescence have been identified, few involving NAD biosynthetic pathways have been described for plants. Here, we report the cloning and characterization of Leaf Tip Senescence 1 (LTS1) in rice (Oryza sativa), a recessive mutation in the gene encoding O. sativa nicotinate phosphoribosyltransferase (OsNaPRT1) in the NAD salvage pathway. A point mutation in OsNaPRT1 leads to dwarfism and the withered leaf tip phenotype, and the lts1 mutant displays early leaf senescence compared to the wild type. Leaf nicotinate and nicotinamide contents are elevated in lts1, while NAD levels are reduced. Leaf tissue of lts1 exhibited significant DNA fragmentation and H 2 O 2 accumulation, along with up-regulation of genes associated with senescence. The lts1 mutant also showed reduced expression of SIR2-like genes (OsSRT1 and OsSRT2) and increased acetylation of histone H3K9. Downregulation of OsSRTs induced histone H3K9 acetylation of senescence-related genes. These results suggest that deficiency in the NAD salvage pathway can trigger premature leaf senescence due to transcriptional activation of senescence-related genes.

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Brevibacillus laterosporus was newly classified from Bacillus laterosporus, which has ability to be used as a biological control agent in crop field. B. laterosporus strain B9 is an aerobic, motile, Gram-positive, spore-forming rod that was isolated from a field of Oryza sativa in Zhejiang, China in 2011. This bacterium has been confirmed to be a strong antagonist against bacterial brown strip of rice caused by Acidovorex avenae subsp. avenae. Here we describe the features of B. laterosporus strain B9, together with the complete genome sequence and its annotation. The 5,272,435bp genome contains 4804 protein-coding genes and 227 RNA-only encoding genes with 2 plasmids.

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Achromobacter insolitus is a newly described, Gram-negative, small (1-2 mm long) and coccoid pathogen that has been isolated from leg wound. Due to its potential threat to human beings, the type strain of this species LMG 6003T was completely sequenced in this study. The genomic analysis revealed that the genome of LMG 6003T consists of one circular DNA chromosome of 6 492 697 bp with a GC content of 65.10%. The entire genome contains 6208 predicted coding genes, 61 tRNAs and 13 rRNA genes. Comparative genome analysis between LMG 6003T and another selected 10 sequenced Achromobacter revealed that 725 genes only exist in LMG 6003T. In particular, these genes include several important pathogenic-related genes such as Type IV prepilin peptidase (TadV/CpaA), Type VI secretion lipoprotein (VasD) and type 1 fimbriae major subunit (FimA). Genomic island (GI) analysis also suggests the existence of GIs in LMG 6003T. All these results strongly suggest the unique genomic features in LMG 6003T against other Achromobacter species. This report will provide us with an extended understanding of A. insolitus at the genomic level and would be helpful for understanding the evolution of the Achromobacter genus.

The objective of the study was to understand the genetic basis of eight traits conferring grain appearance and yield in a recombinant inbred line (RIL8) derived from a cross between cultivated Indica rice varieties Dexiang074B and Pujiang6. We conducted whole genome re‐sequencing for the two parental lines and genotyping by sequencing (GBS) for the RIL8 population. Next, we aligned the clean reads to the rice genome Nipponbare IRGSP 1.0, constructed the genetic linkage map (GLM), and performed the quantitative trait loci (QTL) analysis. In total, 2631 high‐quality markers were generated for 315 RIL8 samples. We identified a rice GLM containing 12 linkage groups (total map distance: 1946.71 cM; average map distance: 0.74 cM) and 98 QTLs related to the rice yield, including 31 high credible QTLs. In addition, 39 QTLs were identified to be associated with the G*E interaction. While most of the QTLs were co‐localized with previously reported rice QTLs, some novel QTLs were identified for the first time in this study. These findings provide a genetic basis for developing cultivated rice with good economic characteristics based on molecular breeding technologies.

Background Signal transduction mediated by heterotrimeric G proteins, which comprise the α, β, and γ subunits, is one of the most important signaling pathways in rice plants. RGA1, which encodes the Gα subunit of the G protein, plays an important role in the response to various types of abiotic stress, including salt, drought, and cold stress. However, the role of RGA1 in the response to heat stress remains unclear. Results The heat-resistant mutant ett1 (enhanced thermo-tolerance 1) with a new allele of the RGA1 gene was derived from an ethane methyl sulfonate-induced Zhonghua11 mutant. After 45 °C heat stress treatment for 36 h and recovery for 7 d, the survival rate of the ett1 mutants was significantly higher than that of wild-type (WT) plants. The malondialdehyde content was lower, and the maximum fluorescence quantum yield of photosystem II, peroxidase activity, and hsp expression were higher in ett1 mutants than in WT plants after 12 h of exposure to 45 °C. The RNA-sequencing results revealed that the expression of genes involved in the metabolism of carbohydrate, nicotinamide adenine dinucleotide, and energy was up-regulated in ett1 under heat stress. The carbohydrate content and the relative expression of genes involved in sucrose metabolism indicated that carbohydrate metabolism was accelerated in ett1 under heat stress. Energy parameters, including the adenosine triphosphate (ATP) content and the energy charge, were significantly higher in the ett1 mutants than in WT plants under heat stress. Importantly, exogenous glucose can alleviate the damages on rice seedling plants caused by heat stress. Conclusion RGA1 negatively regulates the thermo-tolerance in rice seedling plants through affecting carbohydrate and energy metabolism.