Summary Melatonin, a natural phytohormone in plants, plays multiple critical roles in plant growth and stress responses. Although melatonin biosynthesis‐related genes have been suggested to possess diverse biological functions, their roles and functional mechanisms in regulating rice grain yield remain largely unexplored. Here, we uncovered the roles of a caffeic acid O‐methyltransferase (OsCOMT) gene in mediating rice grain yield through dual regulation of leaf senescence and vascular development. In vitro and in vivo evidence revealed that OsCOMT is involved in melatonin biosynthesis. Transgenic assays suggested that OsCOMT significantly delays leaf senescence at the grain filling stage by inhibiting degradation of chlorophyll and chloroplast, which, in turn, improves photosynthesis efficiency. In addition, the number and size of vascular bundles in the culms and leaves were significantly increased in the OsCOMT‐overexpressing plants, while decreased in the knockout plants, suggesting that OsCOMT plays a positive role in vascular development of rice. Further evidence indicated that OsCOMT‐mediated vascular development might owe to the crosstalk between melatonin and cytokinin. More importantly, we found that OsCOMT is a positive regulator of grain yield, and overexpression of OsCOMT increase grain yield per plant even in a high‐yield variety background, suggesting that OsCOMT can be used as an important target for enhancing rice yield. Our findings shed novel insights into melatonin‐mediated leaf senescence and vascular development and provide a possible strategy for genetic improvement of rice grain yield.

Pulmonary artery hypertension (PAH) is a disease with high morbidity and mortality. Cyanidin-3-O-β-glucoside (Cy-3-g), a classical anthocyanin, has a variety of biological effects. The present study evaluated whether Cy-3-g attenuated PAH, and explored the potential mechanism of action. Rats were injected with monocrotaline (MCT; 60 mg per kg of body weight) and then treated with Cy-3-g (200 or 400 mg per kg of body weight) for 4 weeks. Protein expression was determined in vitro in transforming growth factor-β1 (TGF-β1)-mediated human pulmonary arterial smooth muscle cells (SMCs). The results indicated that Cy-3-g significantly inhibited the mean pulmonary artery pressure, right ventricular systolic pressure and right ventricular hypertrophy index, as well as vascular remodeling induced by MCT in PAH rats. Further experiments showed that Cy-3-g suppressed the expression of pro-inflammatory factors and enhanced the levels of anti-inflammatory factors. Cy-3-g blocked oxidative stress and improved vascular endothelial injury. Cy-3-g also reduced the proliferation of SMCs. Furthermore, the MCT-and TGF-β1-induced increase in TGF-β1, phosphorylated (p)-p38 mitogen-activated protein kinase (MAPK) and p-cAMP-response element binding protein (CREB) expression was blocked by Cy-3-g treatment in vivo and in vitro. These results indicated that Cy-3-g could prevent vascular remodeling in PAH via inhibition of the TGF-β1/p38 MAPK/CREB axis.

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The maize (Zea mays L.) ZmCNR13 gene, encoding a protein of fw2.2-like (FWL) family, has been demonstrated to be involved in cell division, expansion, and differentiation. In the present study, the genomic sequences of the ZmCNR13 locus were re-sequenced in 224 inbred lines, 56 landraces and 30 teosintes, and the nucleotide polymorphism and selection signature were estimated. A total of 501 variants, including 415 SNPs and 86 Indels, were detected. Among them, 51 SNPs and 4 Indels were located in the coding regions. Although neutrality tests revealed that this locus had escaped from artificial selection during the process of maize domestication, the population of inbred lines possesses lower nucleotide diversity and decay of linkage disequilibrium. To estimate the association between sequence variants of ZmCNR13 and maize ear characteristics, a total of ten ear-related traits were obtained from the selected inbred lines. Four variants were found to be significantly associated with six ear-related traits. Among them, SNP2305, a non-synonymous mutation in exon 2, was found to be associated with ear weight, ear grain weight, ear diameter and ear row number, and explained 4.59, 4.61, 4.31, and 8.42% of the phenotypic variations, respectively. These results revealed that natural variations of ZmCNR13 might be involved in ear development and can be used in genetic improvement of maize ear-related traits.