小麦NF-Y复合体调控叶片衰老的分子机制

Leaf senescence is synchronized with wheat seed development and grain filling at late development stage. Precocious leaf senescence seriously affects wheat yield and grain quality, while extended leaf functional period and delayed leaf senescence can significantly increase yield and improve quality traits. Nuclear factor Y family genes play important roles in plant development, response to various stresses and other biological processes. However, the function of NF-Y in leaf senescence regulation is still unknown. Senescence-associated TaNF-YB2 was identified in our on-going study. TaNF-YB2 is up-regulated during natural- and dark induced- leaf senescence process. Over-expression of TaNF-YB2 caused delayed leaf senescence in Arabidopsis. Our further functional analyses indicated that TaNF-YB2 inhibited ethylene biosynthesis via directly interaction with CCAAT-boxes of ACC synthase (ACS) genes in Arabidopsis. In this study, the function of TaNF-YB2 gene plays in regulation of leaf senescence will be analyzed. NF-YAs and NF-YBs interact with TaNF-YB2 will be identified, and down-stream target genes of NF-Y complex will be uncovered. The genetic and molecular networks and pathways for the regulation of leaf senescence by NF-Y complex could be deciphered. We will use genetic transformation and association analysis of target gene to analyze the yield and quality traits and evaluate their potential values in wheat breeding. The results of this project will help us to understand function of NF-Y complex on regulation of wheat leaf senescence, to elucidate the molecular mechanisms of leaf senescence, and to analyze the co-relationship between leaf senescence and yield and quality traits. This study may also contribute to efficient manipulation in molecular breeding and genetic improvement in wheat.

小麦生长后期叶片衰老与籽粒形成和灌浆成熟同步进行，叶片过早衰老严重影响产量和品质，而延长叶片功能期则显著改善主要产量品质性状。核因子NF-Y家族在植物发育、逆境胁迫响应等过程发挥功能，但是否参与叶片衰老调控尚不清楚。本实验室前期工作表明，TaNF-YB2在叶片自然衰老和黑暗诱导的衰老过程中上调表达，过表达后推迟叶片衰老的发生；TaNF-YB2可能通过与乙烯生物合成关键酶基因ACS互作，抑制乙烯的生物合成。本项目拟采用多种研究手段系统分析TaNF-YB2在小麦叶片衰老进程调控中的功能；寻找与其互作的NF-YA和NF-YC蛋白及靶基因，解析NF-Y复合体参与的叶片衰老调控网络；采用遗传转化和目标基因关联分析手段，评估其育种价值，探讨该基因与产量品质形成关系。预期研究结果将揭示小麦叶片衰老进程中NF-Y复合体发挥作用的分子机制，为小麦分子育种和遗传改良提供理论依据，具有重要的理论意义和应用前景。

衰老是植物发育的最后阶段，小麦开花后的叶片衰老与籽粒灌浆同步进行，决定了小麦的产量和籽粒营养品质。衰老是生物大分子降解导致的细胞程序性死亡过程，这一过程受基因表达的精细调控，机制十分复杂。NF-Y家族成员在植物发育、胁迫响应等过程中发挥功能，但是否参与叶片衰老调控尚不清楚。本课题组通过转录组数据结合实时定量PCR分析，发现TaNF-YB2基因在小麦旗叶衰老过程中上调表达，且在幼穗、灌浆期籽粒中具有较高表达水平。特别是TaNF-YB2B在灌浆期的转录水平相较于开花期显著性提高，表明其在旗叶衰老启动和籽粒灌浆中发挥重要作用。通过遗传转化，获得了TaNF-YB2基因稳定的过表达转基因小麦和病毒诱导的基因干涉沉默表达小麦株系。过表达植株表现出叶片晚衰的表型，而干涉植株表现为叶片早衰。外源ACC处理可以恢复黑暗诱导TaNF-YB2过表达植株的晚衰表型，表明与乙烯合成相关。同时TaNF-YB2可以回复拟南芥同源基因突变体atnf-yb1的早衰表型，说明NF-Y家族成员在叶片衰老过程中的作用是保守的。通过EMSA、酵母单杂交等实验，我们发现TaNF-YB2可以与小麦乙烯合成关键酶基因TaACS2A、TaACS2B互作，进一步证明了TaNF-YB2通过参与乙烯合成途径调控叶片衰老。在温室和田间两种种植环境下，TaNF-YB2过表达转基因小麦的穗数明显高于野生型。我们正在进行优异单倍型分析和相关产量性状分析。本项目研究结果为揭示TaNF-Y家族调控小麦叶片衰老的分子机制提供理论依据，为基于叶片衰老调控的小麦分子育种提供基因源和材料。