Isolation of cDNAs differentially expressed in response to drought stress and characterization of the Ca-LEAL1 gene encoding a new family of atypical LEA-like protein homologue in hot pepper (Capsicum annuum L. cv. Pukang)

Among various abiotic stresses, water deficit is one of the most severe environmental factors responsible for the reduction of crop yield in many parts of the world. By means of the mRNA differential display technique, seven cDNAs (pCa-DIs for Capsicum annuum drought induced) have been isolated that are rapidly induced when hot pepper plants are subjected to water stress (5-20% loss of fresh weight). For all of the isolated Ca-DIs, database search provided significant sequence similarity to previously described genes from different plant species. The predicted proteins encoded by the Ca-DI genes are putatively involved in processes as diverse as primary metabolism, protein degradation, cell wall modification and stress response, suggesting the complexity of cellular responses to drought stress in hot pepper plants. Particularly, we analyzed the detailed structural property and expression pattern of the Ca-D14 (Ca-LEAL1) gene. Sequence homology studies indicate that Ca-LEAL1 (M(r) = 19.3 kDa) belongs to a new family of atypical hydrophobic late embryogenesis-abundant-like (LEA-like) proteins. Expression analysis showed that Ca-LEAL1 was strongly activated by drought and salt stresses, and also in response to mechanical wounding in both local and systemic leaves. Moreover, the level of Ca-LEAL1 transcript was rapidly enhanced by exogenous application of ABA and ethylene. These results are consistent with the notion that an atypical hydrophobic Ca-LEAL1 protein is subject to control by diverse environmental factors and that ethylene, in conjunction with ABA, plays an important role in the regulation of the stress gene in hot pepper plants. The possible physiological functions of Ca-LEAL1 as well as other Ca-DI proteins in the adaptive process against drought stress are discussed. (C) 2003 Elsevier Ireland Ltd. All rights reserved.