Rizal Govinda, Thakur Vivek, Dionora Jacqueline, Karki Shanta, Wanchana Samart, Acebron Kelvin, Larazo Nikki, Garcia Richard, Mabilangan Abigail, Montecillo Florencia, Danila Florence, Mogul Reychelle, Pablico Paquito, Leung Hei, Langdale Jane A, Sheehy John, Kelly Steven, Quick William Paul
C4 Rice Center, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Plant Breeding, Genetics, and Biotechnology Division, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines.
Plant J. 2015 Oct;84(2):257-66. doi: 10.1111/tpj.13007.
The specification of vascular patterning in plants has interested plant biologists for many years. In the last decade a new context has emerged for this interest. Specifically, recent proposals to engineer C(4) traits into C(3) plants such as rice require an understanding of how the distinctive venation pattern in the leaves of C(4) plants is determined. High vein density with Kranz anatomy, whereby photosynthetic cells are arranged in encircling layers around vascular bundles, is one of the major traits that differentiate C(4) species from C(3) species. To identify genetic factors that specify C(4) leaf anatomy, we generated ethyl methanesulfonate- and γ-ray-mutagenized populations of the C(4) species sorghum (Sorghum bicolor), and screened for lines with reduced vein density. Two mutations were identified that conferred low vein density. Both mutations segregated in backcrossed F(2) populations as homozygous recessive alleles. Bulk segregant analysis using next-generation sequencing revealed that, in both cases, the mutant phenotype was associated with mutations in the CYP90D2 gene, which encodes an enzyme in the brassinosteroid biosynthesis pathway. Lack of complementation in allelism tests confirmed this result. These data indicate that the brassinosteroid pathway promotes high vein density in the sorghum leaf, and suggest that differences between C(4) and C(3) leaf anatomy may arise in part through differential activity of this pathway in the two leaf types.
多年来，植物中维管模式的形成一直吸引着植物生物学家。在过去十年中，这种兴趣有了新的背景。具体而言，最近将C4性状导入水稻等C3植物的提议，需要了解C4植物叶片中独特的叶脉模式是如何确定的。具有花环结构的高叶脉密度，即光合细胞围绕维管束呈环状排列，是区分C4植物和C3植物的主要特征之一。为了鉴定决定C4叶片解剖结构的遗传因素，我们构建了C4植物高粱（Sorghum bicolor）的甲磺酸乙酯和γ射线诱变群体，并筛选叶脉密度降低的株系。鉴定出两个导致低叶脉密度的突变。这两个突变在回交F2群体中均作为纯合隐性等位基因分离。利用下一代测序进行的混合分离分析表明，在这两种情况下，突变表型均与CYP90D2基因的突变有关，该基因编码油菜素类固醇生物合成途径中的一种酶。等位性测试中缺乏互补性证实了这一结果。这些数据表明，油菜素类固醇途径促进高粱叶片的高叶脉密度，并表明C4和C3叶片解剖结构的差异可能部分源于该途径在两种叶片类型中的不同活性。
