Grain shape and size both determine grain weight and therefore crop yield. However, the molecular mechanisms controlling grain shape and size are still largely unknown. Here, we isolated a rice mutant, beak-shaped grain1 (bsg1), which produced beak-shaped grains of decreased width, thickness and weight with a loosely interlocked lemma and palea that were unable to close tightly. Starch granules were also irregularly packaged in the bsg1 grains. Consistent with the lemma and palea shapes, the outer parenchyma cell layers of these bsg1 tissues developed fewer cells with decreased size. Map-based cloning revealed that BSG1 encoded a DUF640 domain protein, TRIANGULAR HULL 1, of unknown function. Quantitative PCR and GUS fusion reporter assays showed that BSG1 was expressed mainly in the young panicle and elongating stem. The BSG1 mutation affected the expression of genes potentially involved in the cell cycle and GW2, an important regulator of grain size in rice. Our results suggest that BSG1 determines grain shape and size probably by modifying cell division and expansion in the grain hull.
We investigated the temporal and spatial changes in cell division, endoreduplication and expression of cell cycle-related genes in developing cucumber fruits at 0-20 days after anthesis (DAA). Cell division was intense at 0-4 DAA and then decreased until to 8 DAA. Meanwhile, endoreduplication started at 4 DAA and increased gradually to 20 DAA, accompanied by an increase in fruit weight. Cell division was mainly observed in the exocarp, while endoreduplication occurred mostly in the endocarp and pulp. Among the six cell cycle-related genes examined, two mitotic cyclin genes (CycA and CycB) and CDKB had the highest transcript levels within 2 DAA, while transcripts of two CycD3 genes and CDKA peaked at 4 DAA and 20 DAA, respectively. Naphthaleneacetic acid (NAA), N-(2-chloro-4-pyridyl)-N'-phenylurea (CPPU) and 24-epibrassinolide (EBR) all induced parthenocarpic growth as well as active cell division, and enhanced transcripts of cell cycle-related genes. In comparison, gibberellic acid (GA(3)) had little effect on the induction of parthenocarpy and transcripts of cell cycle-related genes. These results provide evidence for the important roles of cell division and endoreduplication during cucumber fruit development, and suggest the essential roles of cell cycle-related genes and plant growth substances in fruit development.
BACKGROUND: DNA methylation balance is an important regulatory mechanism for mammalian and plant development. The fruit ripening and anthocyanin accumulation of Vaccinium corymbosum are complex developmental processes that involve numerous physiological, biochemical, and structural alterations. OBJECTIVE: This study aimed to investigate the correlation of DNA methylation balance, DNA methylation and demethylation-related gene expression models and anthocyanin accumulation during blueberry fruit ripening. METHODS: The anthocyanin contents during V. corymbosum ‘O’Neal’ fruit development were evaluated. The V. corymbosum DNA methylation- and anthocyanin accumulation-related genes were isolated, and their relative expression patterns were detected during flower bud enlargement and fruit development. Moreover, the relative expression patterns of anthocyanin biosynthetic genes and the dynamic changes in the DNA methylation of the promoter sequences of key anthocyanin biosynthetic genes were evaluated. RESULTS: The results showed that the DNA methylation level of V. corymbosum fruit was consistent with anthocyanin accumulation during ripening, and the expression levels of anthocyanin biosynthetic and DNA methylation-related genes. CONCLUSIONS: During V. corymbosum fruit ripening, anthocyanin accumulation is regulated partially by DNA methylation balance of VcCHS and VcANS promoters.
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