不同光温条件谷子光温互作模式研究及SiCCT基因表达分析

光周期和温度是影响作物生长发育、生态适应性和产量的2个重要环境因素,揭示光温互作对作物生长发育的效应及其分子机制对育种实践和理论研究具有重要意义。本研究设置长日照高温、长日照低温、短日照高温、短日照低温4个光温处理,调查‘黄毛谷’抽穗期、株高、叶片数和穗长。结果表明,光周期对谷子的发育起关键作用,温度的改变不影响长日照比短日照延迟谷子生殖生长的效应,温度的作用随光周期的不同而异,短日照条件下,高温缩短谷子营养生长期而低温延长营养生长期,长日照条件下则相反;对谷子生殖生长的促迚作用是短日照高温短日照低温长日照低温长日照高温。利用RT-PCR技术从‘黄毛谷’叶片兊隆了一个CCT结构域基因(SiCCT),该基因编码286个氨基酸,属于CMF亚家族成员,基于CCT域基因氨基酸序列的系统迚化分析,谷子与高粱、玉米亲缘关系较近。实时荧光定量PCR分析发现, SiCCT基因在‘黄毛谷’叶片中高表达,其次为幼穗和叶鞘;长日照、短日照处理SiCCT基因均表现24h昼夜节律性特点,短日照七叶期表达水平最高,八叶期(抽穗)及穗后表达迅速降低,长日照七叶至十叶期‘黄毛谷’处于营养生长期,SiCCT基因维持较高表达水平;无论高温低温,长日照条件下SiCCT基因在各叶期表达量整体高于短日照处理,长日照条件下低温处理SiCCT基因的相对表达量明显低于高温处理, SiCCT基因的总体表达量与‘黄毛谷’营养生长期存在正相关。总之SiCCT基因受光周期调控,同时也受温度调控,因而推测SiCCT基因参与了光周期途径和感温性途径,并通过二者互作调控谷子营养生长和生殖生长的全过程。

Photo-thermal interaction model under different photoperiod-temperature conditions and expression analysis of SiCCT gene in foxtail millet (Setaria italica L.)

Photoperiod and temperature are two important environmental factors that affect growth and development, ecological adaptability and yield of crops. Uncovering the effect of interaction between photoperiod and temperature on crop growth and development and the molecular mechanism for this interaction has important influence on breeding practice and theoretical research. In this study, four photo-thermal treatments (long-day and high temperature, long-day and low temperature, short-day and high temperature, short-day and low temperature) were designed to investigate heading stage, plant height, leaf number and panicle length of ‘Huangmaogu’. The photoperiod played a key role on growth of foxtail millet, while changes in temperature had no more effect on delaying reproductive growth by long-day treatment compared with that by short-day treatment. The effect of temperature differed with the difference of photoperiod, high temperature shortened vegetative growth period and low temperature prolonged vegetative growth period under short-day condition, while it was opposite under long-day condition. The effect on reproductive growth was short-day and high temperature treatment > short-day and low temperature treatment > long-day and low temperature treatment > long-day and high temperature treatment. Furthermore, a CCT-motif gene named SiCCT was cloned from leaf of ‘Huangmaogu’ by RT-PCR technology, which encodes 286 aa and belongs to CMF subfamily. Phylogenetic analysis based on aa sequences of CCT-motif genes showed that there existed a close relationship among foxtail millet, sorghum and maize. Real-time PCR analysis showed that the expression level of SiCCT was higher in leaf than in young panicle and leaf sheath. The SiCCT showed a circadian expression pattern under both long-day and short-day conditions. The expression level of SiCCT was the highest at 7-leaf stage, and decreased rapidly at 8-leaf stage (heading) and after heading under short-day condition. The expression of SiCCT maintained high level from 7-leaf stage to 10-leaf stage under long-day condition, during which ‘Huangmaogu’ was at vegetative growth phase. No matter high temperature or low temperature, the expression level of SiCCT at different leaf stages was totally higher in long-day treatment than in short-day treatment, and lower in low temperature than in high temperature under long-day condition. The general expression level of SiCCT was positively correlated with vegetative growth period of ‘Huangmaogu’. In summary, SiCCT is regulated by both photoperiod and temperature, suggesting that SiCCT participates in photoperiod pathway and thermosensory pathway, and regulates the whole vegetative and reproductive growth process of foxtail millet through interaction between the two pathways.