赤霉素生物合成酶基因GhCPS和GhKS参与甲哌鎓对棉花幼苗叶片生长的控制

室内盆栽欣抗4，在棉花幼苗第3片真叶完全展平时(第4叶未展开)叶面喷施甲哌鎓(DPC)，研究DPC对棉花幼苗叶片生长的控制与赤霉素(GA)合成早期关键酶柯巴基焦磷酸合酶(CPS)和内根-贝壳杉烯合酶(KS)基因表达的关系。结果表明，DPC处理显著减小棉花幼苗第3和第4叶的叶面积，第4叶叶面积受控制程度较第3叶大；80 mg L^–1DPC处理的棉花幼苗第3和4叶中GA₄含量分别于处理后4 d和4~6 d显著低于对照；与对照相比，80 mg L^–1 DPC处理的棉花幼苗第3叶中GhCPS和GhKS表达在处理后1~4 d显著降低，而第4叶中GhCPS和GhKS的表达在处理后1~6 d显著降低。由此可见，DPC通过影响GhCPS和GhKS的表达，降低内源活性GA₄的含量，控制棉花幼苗叶片生长，且较幼嫩叶片对DPC较敏感。

GhCPS and GhKS Encoding Gibberellin Biosynthesis Enzymes Involve in Inhibition of Leaf Growth by Mepiquat Chloride in Cotton (Gossypium hirsutum L.)

Ent-copalyl diphosphate synthase (CPS) and ent-kaurene synthase (KS) are the key enzymes involved in the early steps of gibberellin (GA) biosynthesis. This paper aimed at elucidating whether the action of mepiquat chloride (DPC) on leaf growth was related to the expression levels of GhCPS and GhKS in cotton seedlings. DPC was foliar applied to seedlings at the 3rd leaf expanded stage of cotton cultivar Xinkang 4 by pot culture. The results showed that DPC significantly decreased the leaf area, and the area of the 4th leaf was decreased more than that of the 3rd leaf. DPC at 80 mg L^–1 markedly reduced GA₄ content in the 3rd leaf at four days after treatment and in the 4th leaf from four to six days after treatment. The expression levels of GhCPS and GhKS in the 3rd leaf were decreased by DPC from one to four days after treatment, and similar trends were observed in the 4th leaf from one to six days after treatment. All the results suggested that DPC could reduce endogenous GA₄ content by downregulating GhCPS and GhKS expressions, leading to a smaller leaf size. Otherwise, the younger leaf was more sensitive to DPC.