低温与外源ABA对小麦返白系叶绿体基因的表达调控

The wheat albinism strain is a stage albino nature mutant, which induced by continual low temperature, and this albino character is controlled by nuclear and cytoplasmic factors together. Our experiments indicated that, the chloroplast development and metabolism of the mutant is inhibited in the albino stage. Comparing with the mother wheat Aibian 1, there have some change in the nuclear and plastid genes in mutant, and the extro ABA could postpone and lighten the albino phnomena. So, in this project, we will investigate the expression regulation of the chloroplast genome in mutant and related wheat varieties on transcription, after transcription, and especially on translation level, under different cold conditions (day/night 4℃/0℃、2℃/-2℃、2℃/-4℃）to induce albino, then higher temperature to return green, and with serial ABA treatments(15μmol/L、50μmol/L、100μmol/L). The expression patterns of few nuclear candidate genes related to the albino will also be studied. We hope to explain the special expression profiles of chloroplast genome in albino strain, and indentity whether the albino mutant is regulated by the abnormal low temperature sigling pathway that depend on ABA, or by the selected nuclear and cytoplasmic factors. Our final destination is that the genetics, physiological and molecular mechanisms of albino mutation will be fully demonstrated.

小麦返白系是低温诱导叶片阶段性白化的自然突变体，该性状受到核基因与细胞质基因的共同调控。研究表明，返白系在白化阶段的叶绿体发育和代谢受阻，与亲本小麦矮变1号相比：细胞核和叶绿体基因组均发生变异、在室温条件与4℃持续低温处理后叶绿体基因的表达谱表现显著差异，而外源ABA处理可以延缓返白系低温诱导的白化现象。在此基础上，本项目拟研究在不同低温条件（昼/夜 4℃/0℃、2℃/-2℃、2℃/-4℃）诱导白化和温度升高后诱导复绿的过程中、以及不同浓度外源ABA（15μmol/L、50μmol/L、100μmol/L）处理条件下，返白系及相关材料叶绿体基因在转录、转录后、特别是在翻译水平受到的表达调控，同时对一些与白化相关的候选核质基因的表达模式进行研究，深入分析返白系中叶绿体基因表达的特异性，并揭示该白化现象是否与依赖ABA的低温信号传递途径受阻及候选的核质因子有关，进一步阐明返白系白化的遗传、生理和分子机制。

本项目在前期研究的基础上，从低温与外源ABA对返白系中质体基因与核基因表达的影响、质体H2O2的累积与叶片白化现象的相关性、表观遗传调控、叶绿体核糖体组装抑制剂红霉素处理对叶色的影响，以及基因芯片、转录组、蛋白质组分析等方面，更进一步深入研究低温诱导返白系白化的分子机制与遗传机制。主要结果有：（1）低温条件下，外源ABA预处理，补偿了受阻的ABA信号传递通路，并诱导大多数质体基因上调表达，进一步延缓了返白系的白化现象；（2）在低温条件下，返白系中H2O2的累积是叶片白化的重要原因之一；（3）低温诱导返白系叶色白化的现象过程中有表观遗传调控参与；（4）叶绿体核糖体组装或翻译受到影响，可以在常温条件下引起小麦叶色白化；（5）低温诱导白化的现象是可以通过外源花粉杂交后引起，特定的细胞核基因可以引起胞质因子的改变，使后代表现为母系遗传调控的白化现象。经过四年的探索，项目取得了重要的进展，为后续阐明返白系及同类相关材料的白化机制奠定了良好的基础，为进一步研究叶绿体发育、小麦冷驯化与抗寒机制、核质互作、小麦表观遗传调控等提供了新的线索和思路。