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Emergence of a Novel Chimeric Gene Underlying Grain Number in Rice.

ABSTRACT: Grain number is an important factor in determining grain production of rice (Oryza sativa L.). The molecular genetic basis for grain number is complex. Discovering new genes involved in regulating rice grain number increases our knowledge regarding its molecular mechanisms and aids breeding programs. Here, we identified GRAINS NUMBER 2 (GN2), a novel gene that is responsible for rice grain number, from "Yuanjiang" common wild rice (O. rufipogon Griff.). Transgenic plants overexpressing GN2 showed less grain number, reduced plant height, and later heading date than control plants. Interestingly, GN2 arose through the insertion of a 1094-bp sequence from LOC_Os02g45150 into the third exon of LOC_Os02g56630, and the inserted sequence recruited its nearby sequence to generate the chimeric GN2 The gene structure and expression pattern of GN2 were distinct from those of LOC_Os02g45150 and LOC_Os02g56630 Sequence analysis showed that GN2 may be generated in the natural population of Yuanjiang common wild rice. In this study, we identified a novel functional chimeric gene and also provided information regarding the molecular mechanisms regulating rice grain number.

SUBMITTER: Chen H

PROVIDER: S-EPMC5289865 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Emergence of a Novel Chimeric Gene Underlying Grain Number in Rice.

Chen Hao H Tang Yanyan Y Liu Jianfeng J Tan Lubin L Jiang Jiahuan J Wang Mumu M Zhu Zuofeng Z Sun Xianyou X Sun Chuanqing C

Genetics 20161216 2

Grain number is an important factor in determining grain production of rice (Oryza sativa L.). The molecular genetic basis for grain number is complex. Discovering new genes involved in regulating rice grain number increases our knowledge regarding its molecular mechanisms and aids breeding programs. Here, we identified GRAINS NUMBER 2 (GN2), a novel gene that is responsible for rice grain number, from "Yuanjiang" common wild rice (O. rufipogon Griff.). Transgenic plants overexpressing GN2 showe ...[more]

PMID: 27986805

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Project description:Rice yield potential is largely determined by the balance among source capacity, sink strength, and flow fluency. Our previous study indicated that the gene GNP1 encoding gibberellin biosynthesis gene GA20ox1 affects grain number per panicle (GNP) in rice, thus resulting in increase of grain yield. To clarify GNP1 effect on sink, source and flow in regulating rice grain yield, we compared Lemont, a japonica (geng) cultivar, with its near-isogenic line (NIL-GNP1 TQ) in Lemont background with introgression of the allele at GNP1 from Teqing, a high-yielding indica (xian) cultivar. NIL-GNP1 TQ exhibited averagely 32.8% more GNP than Lemont with the compensation by reduced seed setting rate, panicle number and single-grain weight. However, NIL-GNP1 TQ still produced averagely 7.2% higher grain yield than Lemont in two years, mainly attributed to significantly more filled grain number per panicle, and greater vascular system contributing to photoassimilates transport to spikelets. The significantly decreased grain weight of superior spikelets (SS) in NIL-GNP1 TQ was ascribed to a significant decrease of grain size while the significantly decreased grain weight of inferior spikelets (IS) ascribed to both grain size and poor grain-filling as compared with Lemont. The low activities of key enzymes of carbon metabolism might account for the poor grain-filling in IS, which resulted in more unfilled grains or small grain bulk density in NIL-GNP1 TQ. In addition, low seed setting rate and grain weight of IS in NIL-GNP1 TQ might be partially resulted from significantly lower carbohydrate accumulation in culms and leaf sheath before heading compared with Lemont. Our results indicated that significantly increased GNP from introgression of GNP1 TQ into Lemont did not highly significantly improve grain yield of NIL-GNP1 TQ as expected, due primarily to significant low sink activities in IS and possible insufficient source supply which didn't fully meet the increased sink capacity. The results provided useful information for improving rice yield potential through reasonably introgressing or pyramiding the favorable alleles underlying source-related or panicle number traits by marker-assisted selection.

Project description:BackgroundRice tiller number is one of the most important factors that determine grain yield, while nitrogen is essential for the crop growth and development, especially for tiller formation. Genes involved in nitrogen use efficiency processes have been identified in the previous studies, however, only a small number of these genes have been found to improve grain yield by promoting tillering.ResultsWe constructed over-expression (OX) lines and RNA-interference (Ri) lines, and selected a mutant of OsNPF7.2, a low-affinity nitrate transporter. Our analyses showed that rice tiller number and grain yield were significantly increased in OX lines, whereas Ri lines and mutant osnpf7.2 had fewer tiller number and lower grain yield. Under different nitrate concentrations, tiller buds grew faster in OX lines than in WT, but they grew slower in Ri lines and mutant osnpf7.2. These results indicated that altered expression of OsNPF7.2 plays a significant role in the control of tiller bud growth and regulation of tillering. Elevated expression of OsNPF7.2 also improved root length, root number, fresh weight, and dry weight. However, reduced expression of OsNPF7.2 had the opposite result on these characters. OsNPF7.2 OX lines showed more significantly enhanced influx of nitrate and had a higher nitrate concentration than WT. The levels of gene transcripts related to cytokinin pathway and cell cycle in tiller bud, and cytokinins concentration in tiller basal portion were higher in OX lines than that in WT, suggesting that altered expression of OsNPF7.2 controlled tiller bud growth and root development by regulating cytokinins content and cell cycle in plant cells. Altered expression of OsNPF7.2 also was responsible for the change in expression of the genes involved in strigolactone pathway, such as D27, D17, D10, Os900, Os1400, D14, D3, and OsFC1.ConclusionOur results suggested that OsNPF7.2 is a positive regulator of nitrate influx and concentration, and that it also regulates cell division in tiller bud and alters expression of genes involved in cytokinin and strigolactone pathways, resulting in the control over rice tiller number. Since elevated expression of OsNPF7.2 is capable of improving rice grain yield, this gene might be applied to high-yield rice breeding.

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Emergence of a Novel Chimeric Gene Underlying Grain Number in Rice.

Publications

Emergence of a Novel Chimeric Gene Underlying Grain Number in Rice.

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