Gibberellin 20-oxidase promotes initiation and elongation of cotton fibers by regulating gibberellin synthesis.
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.
Xiao
Yue-Hua
YH
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.
Li
De-Mou
DM
Yin
Meng-Hui
MH
Li
Xian-Bi
XB
Zhang
Mi
M
Wang
Yan-Jun
YJ
Dong
Jing
J
Zhao
Juan
J
Luo
Ming
M
Luo
Xiao-Ying
XY
Hou
Lei
L
Hu
Lin
L
Pei
Yan
Y
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D032561:Cotton Fiber; D015870:Gene Expression; D017343:Genes, Plant; D005875:Gibberellins / Q000096:biosynthesis*; D003368:Gossypium / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D056771:Ovule / Q000378:metabolism / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid
D005875:Gibberellins; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)