MERISTEM ACTIVITYLESS (MAL) is involved in root development through maintenance of meristem size in rice

Key message Rice MERISTEM ACTIVITYLESS (MAL) , a RING-H2 finger domain (RFD)-containing gene, regulates meristem cell viability after the initiation of root primordia mediated by cytokinin signaling. Genes in the RING-H2 finger domain (RFD) family play various roles during plant development and in biotic/abiotic stress responses. Rice gene M ERISTEM A CTIVITY L ESS ( MAL ), being contained in the RING-H2 finger domain (RFD), is characterized by a transmembrane domain at the N-terminal and a C3H2C3 zinc finger domain at the C-terminal. To elucidate the physiological and molecular functions of MAL , we generated MAL knockdown transgenic plants by RNA interference. MAL RNA-interfered ( MRi ) transgenic plants exhibited a phenotype with shorter crown root length and lower crown root number, accompanied by a lower cell division rate. The low division rate was observed in the root meristem exactly where MAL was expressed. Furthermore, transcriptome data revealed that cell wall macromolecule metabolism-related genes and redox-related genes were enriched in MAL RNAi lines. Most of these differentially expressed genes (DEGs) were induced by exogenous cytokinin. Hence, we conclude that MAL , as a novel regulatory factor, plays a major role in maintaining cell viability in the meristem after the initiation of root primordial formation, mediated by cytokinin signaling and reactive oxygen species (ROS).