杂种优势是一种重要的生物学现象，对玉米产量的贡献率约占40%。玉米穗长和穗粗等穗部性状的杂种优势是产量形成的重要遗传学基础，而明确其形成的分子机理对优良杂交组合的有效预测与定向组配具有重要意义。课题组前期研究发现，miRNA390是玉米穗部性状杂种优势形成的一个重要调控因子，以miR390-TAS3-ARF24级联调控模式发挥基因的表达调控功能。本研究拟在前期研究的基础上，以miR390-TAS3-ARF24级联通路中3个关键因子的过表达和敲除载体转化阳性事件为材料，通过与不同自交系测交种的穗部性状杂种优势分析，结合基因表达模式确定miR390-TAS3-ARF24调控玉米穗部性状杂种优势的分子机制；并通过遗传学、细胞学、分子生物学和生物信息学分析，建立依赖miR390-TAS3-ARF24级联通路调控雌穗顶端分生组织对生长素信号响应，进而影响玉米穗部性状杂种优势的基因表达调控网络。

Heterosis is of great importance to animal and plant breeding. Maize ear traits heterosis, especially ear diameter and ear length heterosis, contributed over 40% to yield of hybrids. However, the genetic mechanisms explaining ear traits heterosis is far from clearly described. Dissection the genes and mechanisms controlling maize ear traits heterosis will do great help to increase breeding accuracy and efficiency. In a former work, our group had suggested that miR390 is a key regulator of maize ear traits heterosis. Ear degradome sequencing shown that TAS3 is the direct target gene of miR390 that in-turn regulates ARF24 gene expression in post-transcription level. Since maize miR390 regulates down-stream gene expression via miR390-TAS3-ARF24 cascades, in this study, the detailed functions of each member of the cascades will be studied. Over expression and STTM or CRISPR/Cas9 transgenic lines of miR390, TAS3, and ARF24 were to test-cross with 10 maize inbred lines. The ear traits would be measured and compared in hybrids level. Genome wide gene expression, together with genetics, molecular biological, and bioinformatics tools will help to discover the molecular functions of each miR390-TAS3-ARF24 cascades genes and their contributions to maize ear heterosis. Furthermore, the gene regulating networks of miR390-TAS3 -ARF24 cascades that controlling maize ear traits heterosis will be constructed, especially, the roles of Auxin in the regulation network will be discussed.