MERISTEM ACTIVITYLESS ( MAL ) is involved in root development through maintenance of meristem size in rice
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MERISTEM ACTIVITYLESS (MAL) is involved in root development through maintenance of meristem size in rice Wei Jiang1 · Shaoli Zhou1 · Honglin Huang1 · Huazhi Song1 · Qinglu Zhang1 · Yu Zhao1 Received: 12 April 2020 / Accepted: 13 August 2020 © Springer Nature B.V. 2020
Abstract 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. Abstract Genes in the RING-H2 finger domain (RFD) family play various roles during plant development and in biotic/ abiotic stress responses. Rice gene MERISTEM ACTIVITYLESS (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 metabolismrelated 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). Keywords Rice · MAL · Root meristem activity · Cytokinin signaling · ROS
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11103-020-01053-4) contains supplementary material, which is available to authorized users. * Yu Zhao [email protected] Wei Jiang [email protected] Shaoli Zhou [email protected] Honglin Huang [email protected] Huazhi Song [email protected] Qinglu Zhang [email protected] 1
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China
Understanding the mechanisms behind plant root development is important for regulating root growth in order to improve crop performance. The root system of rice is composed of three root types that are formed during consecutive developmental stages. Among these types, crown roots (CRs) [also named shoot-borne roots or adventitious roots (ARs)], which are specific to cereals, initiate from the ground meristem located in stem nodes of coleoptile sections during the postembryonic development process (Marcon et al. 2013) and constitute the main part of the fibrous root system (Zhao et al. 2009). The elongation of crown roots primarily expands the volume of soil explored. It is now widely accepted that many aspects of crown root development, including
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