OsCML4 improves drought tolerance through scavenging of reactive oxygen species in rice

Calmodulin-like (CML) genes function in regulating plant responses to different abiotic stresses, such as high salt and drought. Using japonica type rice seedlings ('Nipponbare'), we induced the expression of OsCML4 (Accession No. NM_001057768), which encodes a rice CML protein. Under drought conditions, transgenic plants over-expressing that gene exhibited obviously improved growth performance and higher survival rates than the wild type (WT). Activity by reactive oxygen species (ROS)- scavenging enzymes superoxide dismutase (SOD) and catalase (CAT), as well as proline concentrations, were significantly increased in transgenic plants. Expression by ROS scavenging-related genes APXI and Cat-B and the stress-related gene OsP5CS1 was also enhanced in the transgenics under drought conditions. However, the sensitivity to abscisic acid (ABA) was similar between over-expressing and WT plants. These results suggest that OsCML4 confers drought tolerance partially through ROS-scavenging and also by inducing other stress-related genes in an ABAindependent manner.