Abstract:

Calmodulin is a ubiquitous transducer of calcium signals in eukaryotes. It mediates a lot of cellular processes, such as transcription, cytoskeletal organization and motility, and amino acid metabolism. In diploid plant species, several isoforms of calmodulin have been described. A novel CaM gene was isolated from cDNA library of wheat leaves infected by Puccinia striiformis f. sp. tritici through RT-PCR approach. The gene was tentatively designated as TaCaM5 and encoded a novel CaM isoform based on protein sequence analysis. The open reading frame of TaCaM5 was 450 bp in length and 149 amino acids were encoded with four conserved EF-hand domains. TaCaM5, in which transmembrane domain or signal peptide sequence was absent, was predicted existing in cytoplasm. The amino acid sequence of TaCaM5 shares 97% identify with ZmCaM from Zea mays. TaCaM5 expressed differently in the wheat leaf, stem, and root. Challenged by stripe rust fungus(Puccinia striiformis f. sp. tritici), TaCaM5 was induced by this fungus in both incompatible and compatible interactions, with the maximal expression at 6 h and 24 h post inoculation respectively. TaCaM5 was up-regualted by exogenous abscisic acid, ethylene and jasmonic acid and down-regulated by salicylic acid. TaCaM5 was obviously up-regulated by various abiotic stresses, such as low temperature, mechanical wound, and drought. However, high salinity stress could not induce the expression of TaCaM5. These results suggest that TaCaM5 is probably involved in regulating the host defence responses through ethylene and jasmonic acid pathways, and also participate in Ca²⁺-CaM signal transmission pathways under mechanical wound, low temperature, and drought conditions.

Key words: Wheat Stripe rust, CaM isoform, Abiotic stress, qRT-PCR