Seed size is a key agronomic trait that greatly determines plant yield. Elucidating the molecular mechanism underlying seed size regulation is also an important question in developmental biology. Recently, a study conducted by Prof. LI Yunhai’s team at Institute of Genetics and Developmental Biology of Chinese Academy of Sciences shows that the KIX-PPD-MYC-GIF1 pathway plays a crucial role in seed size control in Arabidopsis thaliana. Disruption of KIX8/9 and PPD1/2 causes large seeds due to increased cell proliferation and cell elongation in the integuments. KIX8/9 and PPD1/2 interact with transcription factors MYC3/4 to form the KIX-PPD-MYC complex in Arabidopsis. The KIX-PPD-MYC complex associates with the typical G-box sequence in the promoter of GRF-INTERACTING FACTOR 1 (GIF1), which promotes seed growth, and represses its expression. Genetic analyses support that KIX8/9, PPD1/2, MYC3/4, and GIF1 function in a common pathway to control seed size. Thus, the results reveal a genetic and molecular mechanism by which the transcription factors MYC3/4 recruit KIX8/9 and PPD1/2 to the promoter of GIF1 and repress its expression, thereby determining seed size in Arabidopsis.
The study was published in Nature Communications on April 15. Dr. LIU Zupei graduated from University of Chinese Academy of Sciences (Institute: Institute of Genetics and Developmental Biology of Chinese Academy of Sciences) is the first author, Prof. LI Yunhai is the corresponding author. This work was supported by the grants from National Natural Science Foundation of China, the National Special Project, and the strategic priority research program of the Chinese Academy of Sciences.