Beyond the phloem: A general role of the ArabidopsisOCTOPUSgene family in controlling plant growth vigour

Abstract

SummaryOCTOPUS(OPS) andOCTOPUS-LIKE 2(OPL2), two homologous genes, were previously identified as important regulators of phloem differentiation in Arabidopsis roots, impacting root growth when their function is lost. Here, we investigated the roles of the other threeOPShomologs in Arabidopsis,OPL1,OPL3, andOPL4. We employed promoter activity analyses, protein localisation studies, functional complementation assays, analysis of single and multiple mutant combinations, and growth assays, including exposure to CLE45 and brassinosteroid pathway modulators. TheOPS/OPLgenes exhibit overlapping expression patterns and functions. Multiple mutant combinations revealed a high degree of redundancy, withOPSand the phloem domain playing a major role in controlling plant growth. While phloem phenotypes are not exacerbated in higher-order mutants, plant growth vigour is nevertheless more severely impacted than inops opl2. Our results suggest a novel role of theOPS/OPLgenes in broadly controlling plant growth and development, potentially through the modulation of meristematic activity via brassinosteroid pathways.