SIAMESE-RELATED1 (SMR1) has roles in leaf growth repression under drought (OA)

The cell cycle of plants is regulated by signals that integrate endogenous and environmental cues to allow for adaptation to varying conditions. When a plant is under drought stress, cell division in young leaves is stopped by an active mechanism to conserve resources. Cyclin-dependent kinase-inhibitory proteins (CKIs) have been studied in relation to cell cycle regulation but little is known about their function under stressful conditions. Dubois and colleagues use expression studies, mutant analysis and protein studies to examine the role of the Arabidopsis CKI gene SIAMESE-RELATED1 (SMR1) under drought stress. In young leaves, SMR1 expression is induced by drought and SMR1 inhibits cell division and modifies meristem activity. SMR1 is a short-lived protein that is degraded by the 26S proteasome after being ubiquitinated. The over-expression of a more stable SMR1 protein in Arabidopsis leads to a stronger phenotype (i.e. greater growth inhibition under drought stress). The SMR1 protein may act as a negative regulator of cell division of leaves and roots. (Summary by Julia Miller) Plant Phys. 10.1104/pp.17.01712