Key Laboratory of Biotechnology and Crop Quality Improvement of Ministry of Agriculture of China, Biotechnology Research Center (Southern Campus), Southwest University, Tiansheng Road 216, Beibei, Chongqing 400716, PR China.
J Plant Physiol. 2010 Jul 1;167(10):829-37. doi: 10.1016/j.jplph.2010.01.003. Epub 2010 Feb 9.
Cotton is the leading natural fiber, and gibberellin (GA) is a phytohormone involved in the development of cotton fibers. However, it is largely unknown how the GA content in ovules and fibers is regulated and how the endogenous GA concentration affects fiber development. To address these questions, three GA 20-oxidase homologous genes (GhGA20ox1-3) were cloned and the endogenous bioactive GA content in developing ovules and fibers determined by liquid chromatography-electrospray ionization-mass spectrometry. Real-time reverse transcription PCR (RT-PCR) revealed that GhGA20ox1 expressed preferentially in elongating fibers and that the expression level varied with the endogenous GA content consistently, while GhGA20ox2 and GhGA20ox3 transcripts accumulated mainly in ovules. The GA accumulation kinetics as well as the GhGA20ox expression differed in ovules and the attached fibers, suggesting relatively independent GA regulation system in these two sites. Transgenic cotton, over-expressing GhGA20ox1, showed GA over-production phenotypes with increased endogenous GA levels (especially GA(4)) in fibers and ovules. It also produced significantly more fiber initials per ovule, and fiber lengths was increased compared with the control, which demonstrates that up-regulation of the GhGA20ox1 gene promoted fiber initiation and elongation. Our results suggest that GA 20-oxidase is involved in fiber development by regulating GA levels, and corresponding genes might be employed as target genes for the manipulation of fiber initiation and elongation in cotton.
棉花是主要的天然纤维，赤霉素（GA）是一种参与棉花纤维发育的植物激素。然而，胚珠和纤维中 GA 含量是如何调控的，以及内源性 GA 浓度如何影响纤维发育，在很大程度上还不清楚。为了解决这些问题，克隆了三个赤霉素 20-氧化酶同源基因（GhGA20ox1-3），并通过液相色谱-电喷雾电离-质谱法测定了发育中的胚珠和纤维中的内源性生物活性 GA 含量。实时反转录 PCR（RT-PCR）显示，GhGA20ox1 在伸长纤维中优先表达，其表达水平与内源性 GA 含量一致，而 GhGA20ox2 和 GhGA20ox3 转录物主要在胚珠中积累。胚珠和附着纤维中的 GA 积累动力学以及 GhGA20ox 表达不同，表明这两个部位存在相对独立的 GA 调控系统。过表达 GhGA20ox1 的转基因棉花表现出 GA 过度产生的表型，纤维和胚珠中的内源性 GA 水平（特别是 GA(4)）增加。与对照相比，每个胚珠的纤维起始数也显著增加，纤维长度增加，这表明 GhGA20ox1 基因的上调促进了纤维起始和伸长。我们的研究结果表明，GA 20-氧化酶通过调节 GA 水平参与纤维发育，相应的基因可能被用作棉花纤维起始和伸长的操作靶标。
