NAKED ENDOSPERM1, NAKED ENDOSPERM2, and OPAQUE2 interact to regulate gene networks in maize endosperm development

Three maize transcription factors interact and regulate a dynamic gene network that inhibits cellular development and promotes storage compound accumulation at grain filling. NAKED ENDOSPERM1 (NKD1), NKD2, and OPAQUE2 (O2) are transcription factors important for cell patterning and nutrient storage in maize (Zea mays) endosperm. To study the complex regulatory interrelationships among these 3 factors in coregulating gene networks, we developed a set of nkd1, nkd2, and o2 homozygous lines, including all combinations of mutant and wild-type genes. Among the 8 genotypes tested, we observed diverse phenotypes and gene interactions affecting cell patterning, starch content, and storage proteins. From similar to 8 to similar to 16 d after pollination, maize endosperm undergoes a transition from cellular development to nutrient accumulation for grain filling. Gene network analysis showed that NKD1, NKD2, and O2 dynamically regulate a hierarchical gene network during this period, directing cellular development early and then transitioning to constrain cellular development while promoting the biosynthesis and storage of starch, proteins, and lipids. Genetic interactions regulating this network are also dynamic. The assay for transposase-accessible chromatin using sequencing (ATAC-seq) showed that O2 influences the global regulatory landscape, decreasing NKD1 and NKD2 target site accessibility, while NKD1 and NKD2 increase O2 target site accessibility. In summary, interactions of NKD1, NKD2, and O2 dynamically affect the hierarchical gene network and regulatory landscape during the transition from cellular development to grain filling in maize endosperm.

Automated summary

The maize transcription factors NKD1, NKD2, and O2 interact and regulate a dynamic gene network that inhibits cellular development and promotes storage compound accumulation during grain filling. The regulatory interrelationships and genetic interactions among these factors are dynamic and play a crucial role in directing cellular development and controlling the biosynthesis and storage of starch, proteins, and lipids in maize endosperm.