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異源三聚體GTP結合蛋白(G蛋白)和細胞分裂素在調節植物生長發育中起著重要作用。然而,人們對它們協調調節水稻籽粒大小的機制知之甚少。
本研究對一個編碼A、G、γ亞基的基因Rgg1進行了功能鑑定。在幼穗和小穗中檢測到較強的GUS染色,表明該基因在調節穗部相關性狀發育中起作用。Rgg1在日本晴(Nip)和武雲粳30(WYJ30)中過表達,通過調節細胞分裂,顯著降低了株高、穗長和粒長。然而,CRISPR/Cas9系統產生的Rgg1突變體沒有明顯的表型差異,這可能是由於該基因在體內的表達水平極低所致。
RGG1編碼a型Gγ亞基
對NIP幼穗、NIP-Rgg1-2突變體和NIP-OE2過表達系的轉錄本進行了測序,結果表明許多差異表達基因(Deg)與細胞分裂素生物合成途徑相關。我們通過測定內源細胞分裂素水平證實了這一結果,並發現在過表達的品系中細胞分裂素含量較低。
此外,Rgg1的表達增加降低了對低濃度6-苄氨基嘌呤(6-BA)的敏感性。
我們的結果揭示了一個新的控制水稻籽粒大小的G蛋白-細胞分裂素模塊,這將有助於理解G蛋白調節籽粒大小和植株發育的機制。
Heterotrimeric GTP binding proteins (G proteins) and cytokinin play important roles in regulating plant growth and development. However, little is known about the mechanism by which they coordinate the regulation of grain size in rice. We functionally characterized one gene, RGG1, encoding a type-A Gγ subunit. Strong GUS staining was detected in young panicles and spikelets, suggesting a role for this gene in modulating panicle-related trait development. Overexpression of RGG1 in Nipponbare (NIP) and Wuyunjing 30 (WYJ30) significantly decreased plant height, panicle length and grain length by regulating cell division. However, rgg1 mutants generated by the CRISPR/Cas9 system exhibited no obvious phenotypic differences, which may be due to the extremely low expression level of this gene in vivo. The transcriptomes of young panicles of NIP, the NIP-rgg1–2 mutant and the NIP-OE2 overexpression line were sequenced, and the results showed that many differentially expressed genes (DEGs) were associated with the cytokinin biosynthetic pathway. We confirmed this result by measuring the endogenous cytokinin levels and found that cytokinin content was lower in the overexpression lines. Additionally, increased expression of RGG1 decreased sensitivity to low concentrations of 6-benzylaminopurine (6-BA). Our results reveal a novel G protein—cytokinin module controlling grain size in rice and will be beneficial for understanding the mechanisms by which G proteins regulate grain size and plant development.
Yajun Tao, Jun Miao, Jun Wang, et al. RGG1 , Involved in the Cytokinin Regulatory Pathway, Controls Grain Size in Rice. Rice, 2020