Zhu Qian-Hao, Zhang Jian, Liu Dexin, Stiller Warwick, Liu Dajun, Zhang Zhengsheng, Llewellyn Danny, Wilson Iain
CSIRO Agriculture, Black Mountain Laboratories, ACT 2601, Australia
CSIRO Agriculture, Black Mountain Laboratories, ACT 2601, Australia College of Agronomy and Biotechnology, Southwest University, Chongqing 400716, PR China.
J Exp Bot. 2016 Feb;67(3):763-74. doi: 10.1093/jxb/erv494. Epub 2015 Nov 12.
Diverse leaf morphology has been observed among accessions of Gossypium hirsutum, including okra leaf, which has advantages and disadvantages in cotton production. The okra leaf locus has been mapped to chromosome 15 of the Dt subgenome, but the underlying gene has yet to be identified. In this study, we used a combination of targeted association analysis, F2 population-based fine mapping, and comparative sequencing of orthologues to identify a candidate gene underlying the okra leaf trait in G. hirsutum. The okra leaf gene identified, GhOKRA, encoded a homeodomain leucine-zipper class I protein, whose closely related genes in several other plant species have been shown to be involved in regulating leaf morphology. The transcript levels of GhOKRA in shoot apices were positively correlated with the phenotypic expression of the okra leaf trait. Of the multiple sequence variations observed in the coding region among GrOKRA of Gossypium raimondii and GhOKRA-Dt of normal and okra/superokra leaf G. hirsutum accessions, a non-synonymous substitution near the N terminus and the variable protein sequences at the C terminus may be related to the leaf shape difference. Our results suggest that both transcription and protein activity of GhOKRA may be involved in regulating leaf shape. Furthermore, we found that non-reciprocal homoeologous recombination, or gene conversion, may have played a role in the origin of the okra leaf allele. Our results provided tools for further investigating and understanding the fundamental biological processes that are responsible for the cotton leaf shape variation and will help in the design of cotton plants with an ideal leaf shape for enhanced cotton production.
在陆地棉种质资源中观察到了多种叶形态，包括秋葵叶，其在棉花生产中有优点也有缺点。秋葵叶基因座已被定位到Dt亚基因组的第15号染色体上，但潜在基因尚未确定。在本研究中，我们结合靶向关联分析、基于F2群体的精细定位以及直系同源基因的比较测序，来鉴定陆地棉秋葵叶性状的候选基因。鉴定出的秋葵叶基因GhOKRA编码一种I类同源异型域亮氨酸拉链蛋白，在其他几种植物物种中与其密切相关的基因已被证明参与调节叶形态。GhOKRA在茎尖的转录水平与秋葵叶性状的表型表达呈正相关。在雷蒙德氏棉的GrOKRA以及正常叶和秋葵叶/超级秋葵叶陆地棉种质的GhOKRA-Dt编码区观察到的多个序列变异中，靠近N端的一个非同义替换和C端可变的蛋白质序列可能与叶形差异有关。我们的结果表明，GhOKRA的转录和蛋白质活性可能都参与调节叶形。此外，我们发现非相互同源重组或基因转换可能在秋葵叶等位基因的起源中发挥了作用。我们的结果为进一步研究和理解导致棉花叶形变异的基本生物学过程提供了工具，并将有助于设计具有理想叶形以提高棉花产量的棉花植株。
