MAIN‐LIKE1 is a crucial factor for correct cell division and differentiation in Arabidopsis thaliana

Abstract

SUMMARYPlant development requires accurate coordination of gene expression, both in actively dividing meristematic cells and differentiated cells. Cell fate establishment and maintenance, among others, are mediated by chromatin organization complexes that determine the stable transcriptional states of specific cell types. Here, we focus on MAIN-LIKE1 (MAIL1), one of three homologs of MAINTENANCE OF MERISTEMS (MAIN), which form a plant-specific gene family in Arabidopsis thaliana. We show that MAIL1 encodes a ubiquitously expressed nuclear protein. A mail1 loss-of-function mutant developed short primary roots, in which the meristematic cells accumulated DNA double-strand breaks and underwent massive cell death. In addition, mail1 mutant showed also cell differentiation defects in root and shoot tissues, and developed disorganized callus-like structures. The genetic interaction between main and mail1 mutants suggests that they act in the same pathway, and that both are essential for maintaining correct cell division acitivity in meristematic cells, while MAIL1 has an additional function in differentiating cells.

Arabidopsis proteins with a transposon-related domain act in gene silencing

“…Mapping-by-sequencing indicated that kun contained a mutation in AT2G25010 ( MAINTENANCE OF MERISTEMS-LIKE1 , MAIL1 ; Supplementary Fig. 2a,b), reported to play a role in cell division and differentiation, especially in meristematic cells24. We confirmed a causal role of MAIL1 in L5 silencing by crossing the transgene to an independent mail1 knockout mutation (Fig.…”

“…MAIN, MAIL1 and MAIL2 are highly similar, while MAIL3 contains an additional serine/threonine phosphatase domain24. Analysis of mutants and RNAi lines did not suggest a role of MAIL2 or MAIL3 in gene silencing (Supplementary Fig.…”

“…3). There was no obvious cell death in mail1-2 and in young leaves of either mail1 mutant, but mature mail1-1 leaves suffered from pronounced cell death around the vascular tissue24 (Supplementary Fig. 3).…”

“…Assuming equal DNA content, these data support a role of MAIL1 in condensation of pericentromeric heterochromatin. MAIL1 is a nuclear protein24, and analysis of a MAIL1-GFP fusion protein suggested that MAIL1 is not preferentially associated with chromocenters (Supplementary Fig. 16).…”

“…In Arabidopsis thaliana, MAIL1 is part of a small gene family comprising three other genes, MAIL2, MAIL3 and MAINTENANCE OF MERISTEMS (MAIN) , which encode proteins with a so-called aminotransferase-like, plant mobile domain (PMD)2430. MAIN, MAIL1 and MAIL2 are highly similar, while MAIL3 contains an additional serine/threonine phosphatase domain24.…”