OsMADS14 and NF-YB1 cooperate in the direct activation of OsAGPL2 and Waxy during starch synthesis in rice endosperm (New Phytol.)

Rice grain is mainly composed of starch, which provides the necessary energy and sugars for successful germination and seedling development. Since rice is the most widely consumed crop, studying the regulators that control starch synthesis is crucial to ensure food security for more than half the world‘s population. In monocotyledonous species like rice, FUL-like proteins have been suggested to play a role during grain development, which includes several MADS-domain transcription factors (OsMADS). In this article, Feng et al. dissect the regulatory mechanisms for which OsMADS14 regulates the synthesis of starch during the grain filling process in rice. First, they found that two OsMADS14 loss-of-function mutant lines  produce severely defective grain phenotypes. Through an RNA-Seq analysis, they identified genes repressed in the mutant lines including ADP-GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT 2 (OsAGPL2) and Waxy (Wx). Both genes are directly regulated by OsMADS14. Through protein-protein interaction techniques NF-YB1 (a seed-specific transcription factor) was proposed to associate with OsMADS14 to directly promote OsAGPL2 and Wx gene expression. This work shows how the OsMADS14/ NF-YB1 complex directly regulates core starch synthesis genes. (Summary by Eva Maria Gomez Alvarez, @eva_ga96) New Phytol. 10.1111/nph.17990