玉米是我国重要的饲料和粮食作物，但籽粒缺乏必需氨基酸，严重影响了它的营养品质。胚乳是籽粒最大组成部分，重点关注胚乳灌浆期发生的一系列生物学问题对品质改良尤为重要。优质蛋白玉米营养价值极高，但修饰因子身份及作用机理未知，极大阻碍了新品种开发。申请人拟开展工作的主要科学问题是优质蛋白玉米如何通过积累数量遗传的修饰因子，把软质胚乳o2突变体恢复成硬质高赖氨酸玉米的。申请人团队将通过基因组关联分析、转录组差异比较以及转基因验证来鉴定修饰因子，并运用分子、生化与细胞生物学手段来解析它们的作用机理。团队的长期目标是通过解析这些从胚乳灌浆期重要事件中反复凝练出的基本科学问题，为将来培育高产优质玉米服务。申请人近几年在Nature Communications、PNAS、Plant Physiology及Genetics等杂志发表第一作者文章10篇，积累了丰富的遗传材料，为下一步工作开展奠定了坚实基础。

Maize is one of the most important feed and food crops in China. However, essential amino acids like lysine and tryptophan are deficient in its seed, which substantially compromises its nutrition quality. Endosperm is the largest part of maize seed, so research focusing on endosperm development especially during the filling stage is very critical for genetic improvement in nutrition quality. Quality protein maize (QPM) is a hard version of o2 mutant with nearly doubled levels of lysine, therefore has significantly higher nutrition value than regular maize. However, lack of knowledge in the identities of o2 modifiers, which convert soft endosperm of o2 into hard texture, and their acting mechanisms has greatly impeded the development of new QPM varieties. The applicant’s interest will be focusing on the basic questions: What are the genetic identities of the quantitative o2 modifiers? What are the mechanisms through which the o2 modifiers convert soft endosperm into hard version? The applicant’s group will take advantage of GWAS, transcriptome analysis and gene transformation to characterize and confirm the o2 modifiers, and will use molecular, biochemical and cell biological approaches to dissecting their functions and pathways that they are involved in. Our long-term goal is to booster development of new maize varieties with high yield and nutrition through accumulating knowledge from dissecting the basic scientific questions arising from series of important events in endosperm development during the filling stage. The applicant has productive publications in this area during the past several years, such as Nature Communications, PNAS, Plant Physiology and Genetics, and as a result accumulated a large number of useful genetic materials and constructed many highly effective analysis platforms, which will in turn facilitate the future work.

玉米是我国重要的饲料和粮食作物，但籽粒缺乏必需氨基酸，严重影响了它的营养品质。胚乳是籽粒最大组成部分，重点关注胚乳灌浆期发生的一系列生物学问题对品质改良尤为重要。玉米胚乳主要储存蛋白是醇溶蛋白，即zein，占总蛋白60%以上。Zein根据氨基酸同源性分为α（19和22-kD），γ（50，27和16-kD），β（15-kD）和δ（18和10-kD）四个亚家族。Zein基因家族表达有三个特征：转录水平极高，空间和时间表达非常特异（授粉后10天在胚乳特异表达）。所有zein都几乎不含必需氨基酸赖氨酸和色氨酸，因此玉米胚乳总蛋白中的这两种必需氨基酸含量就极度缺乏。opaque2 (O2)是第一个被鉴定的调控醇溶蛋白表达的转录因子，属于bZIP转录因子家族，通过结合到顺式作用元件O2-box，启动22-kD α-zein等的表达。优质蛋白玉米以o2粉质突变体为高赖氨酸供体，通过聚合胚乳修饰因子恢复成硬质表型而育成。优质蛋白玉米营养价值极高，但修饰因子身份及作用机理未知，极大阻碍了新品种开发。我们围绕玉米蛋白品质问题，开展的研究内容包括玉米储存蛋白基因表达调控网络研究，优质蛋白玉米胚乳修饰因子克隆和功能解析及影响玉米胚乳发育与产量、品质形成的关键基因克隆与功能解析。我们通过基因组关联分析、转录组差异比较以及转基因验证来鉴定修饰因子，并运用分子、生化与细胞生物学手段来解析它们的作用机理。在优青执行期间，我们取得了以下重要结果：1、解析玉米蛋白品质形成的转录调控基础，建立醇溶蛋白基因家族主要调控网络；2、解析优质蛋白玉米胚乳修饰分子遗传机制，克隆了主效修饰因子qγ27，为优质蛋白玉米分子育种开发了可靠的分子标记；3、解析O2和PBF参与玉米品质和粒重形成的平衡机制，提出了更优越的优质蛋白玉米培育方法，为高产优质蛋白玉米分子育种奠定了新的理论基础。我们在优青项目资助下发表4篇SCI论文，其中1篇Plant Cell，2篇PNAS和1篇Genetics，此外还发表1篇书章节。