Conserved functional control, but distinct regulation, of cell proliferation in rice and <i>Arabidopsis</i> leaves revealed by comparative analysis of <i>GRF-INTERACTING FACTOR 1</i> orthologs

Abstract

Regulation of cell proliferation is crucial for establishing the shape of plant leaves. We have identified <i>MAKIBA3</i> (<i>MKB3</i>), a loss-of-function mutant of which exhibits a narrowed- and rolled-leaf phenotype in rice. <i>MKB3</i> was found to be an ortholog of <i>Arabidopsis ANGUSTIFOLIA3</i> (<i>AN3</i>), which positively regulates cell proliferation. The reduced leaf size of <i>mkb3</i> plants with enlarged cells and the increased size of <i>MKB3-</i>overexpressing leaves with normal-sized cells indicate that <i>MKB3</i> is a positive regulator of leaf proliferation and that <i>mkb3</i> mutation triggers a compensation syndrome, as does <i>Arabidopsis an3</i> Expression analysis revealed that <i>MKB3</i> is predominantly expressed on the epidermis of leaf primordia, which is different from the location of <i>AN3</i> A protein movement assay demonstrated that MKB3 moves from an <i>MKB3-</i>expressing domain to a non-expressing domain, which is required for normal leaf development. Our results suggest that rice <i>MKB3</i> and <i>Arabidopsis AN3</i> have conserved functions and effects on leaf development. However, the expression pattern of <i>MKB3</i> and direction of protein movement are different between rice and <i>Arabidopsis</i>, which might reflect differences in leaf primordia development in these two species.