Architecture of the rice inflorescence, which is determined mainly by the morphology, number and length of primary and secondary inflorescence branches, is an important agronomical trait. In the current study, we characterized a novel dense and erect panicle (EP) mutant, dep3, derived from the Oryza sativa ssp. japonica cultivar Hwacheong treated with N-methyl-N-nitrosourea. The panicle of the dep3 mutant remained erect from flowering to full maturation, whereas the panicle of the wild type plant began to droop after flowering. The dep3 mutation also regulated other panicle characteristics, including panicle length, grain shape and grain number per panicle. Anatomical observations revealed that the dep3 mutant had more small vascular bundles and a thicker culm than wild type plants, explaining the EP phenotype. Genetic analysis indicated that the phenotype with the dense and EP was controlled by a single recessive gene, termed dep3. The DEP3 gene was identified as the candidate via a map-based cloning approach and was predicted to encode a patatin-like phospholipase A2 (PLA2) superfamily domain-containing protein. The mutant allele gene carried a 408 bp genomic deletion within LOC_Os06g46350, which included the last 47 bp coding region of the third exon and the first 361 bp of the 3′-untranslated region. Taken together, our results indicated that the patatin-like PLA2 might play a significant role in the formation of vascular bundles, and that the dep3 mutant may provide another EP resource for rice breeding programs.
水稻穗型是一個(gè)重要的農(nóng)藝性狀，主要由一次枝梗和二次枝梗的形態(tài)、數(shù)量和長度決定。在本文中，我們使用N-甲基-N-亞硝基脲處理粳稻品種Hwacheong，分離得到一種新型的直立型密穗突變體dep3。dep3突變體的穗從開花到完全成熟都保持直立狀態(tài)，而野生型植株的稻穗在花后就開始下垂。dep3突變體的穗長、粒形以及每穗粒數(shù)等性狀也發(fā)生了改變。解剖觀察發(fā)現(xiàn)，與野生型相比，dep3突變體的維管束更小、莖更粗，這解釋了穗直立的表型。遺傳學(xué)分析表明直立型密穗表型是由一個(gè)單獨(dú)的隱性基因dep3控制。通過圖位克隆技術(shù)鑒定出候選基因DEP3，預(yù)測(cè)其編碼一個(gè)含有馬鈴薯糖蛋白樣磷脂酶A2（PLA2）超家族結(jié)構(gòu)域的蛋白。突變體等位基因在LOC_Os06g46350處缺失408bp，包括第3外顯子編碼區(qū)的后47bp以及3'端的非翻譯區(qū)的前361bp。綜上所述，我們的結(jié)果表明，PLA2可能在維管束形成中發(fā)揮重要作用。dep3突變體也許可以為水稻育種提供新的EP資源。
結(jié)果：dep3突變體表型描述；dep3突變體在最上部的節(jié)間有更多的維管束；dep3突變體的遺傳學(xué)分析；DEP3基因的精細(xì)繪圖；PLA2是DEP3的一個(gè)候選基因