Identification of Saccharum CaM gene family and functioncharacterization of ScCaM1 during cold and oxidant exposure in Pichia pastoris.

Abstract

Calmodulin (CaM) plays an essential role in binding calcium ions and mediating the interpretation of Ca2+signals in plants under various stresses. However, the evolutionary relationship of CaM family proteins inSaccharumhas not been elucidated. To deduce and explore the evolution and function ofSaccharumCaM family. A total of 104 typical CaMs were obtained fromSaccharum spontaneumand other 18 plant species. The molecular characteristics and evolution of those CaM proteins were analyzed. A typicalCaMgene,ScCaM1, was subsequently cloned from sugarcane (Saccharumspp. hybrid). Its expression patterns in different tissues and under various abiotic stresses were assessed by quantitative real-time PCR. Then the green fluorescent protein was used to determine the subcellular localization of ScCaM1. Finally, the function ofScCaM1was evaluated via heterologous yeast expression systems. Three typical CaM members (SsCaM1, SsCaM2, and SsCaM3) were identified from theS. spontaneumgenome database.CaMs were originated from the two last common ancestors before the origin of angiosperms. The number of CaM family members did not correlate to the genome size but correlated with allopolyploidization events. TheScCaM1was more highly expressed in buds and roots than inother tissues. The expression patterns ofScCaM1suggested that it was involved in responses to various abiotic stresses in sugarcane via different hormonal signaling pathways. Noteworthily, its expression levels appeared relatively stable during the cold exposure in the cold-tolerant variety but significantly suppressed in the cold-susceptible variety. Moreover,therecombinant yeast (Pichia pastoris) overexpressingScCaM1grew better than the wild-type yeast strain under cold and oxidative stresses. It was revealed that theScCaM1played a positive role in reactive oxygen species scavenging and conferred enhanced cold and oxidative stress tolerance to cells. This study provided comprehensive information on the CaM gene family inSaccharumand would facilitate further investigation of their functional characterization.