Abstract
Calmodulins (CaMs), ubiquitous Ca2+ binding proteins in eukaryotes, are consisted of multiple isoforms in plants. It is suggested that plant CaM isoforms may play different roles in the plant cells because (1) these isoforms activate specific target enzymes in vitro respectively (2) they require different Ca2+ concentrations to activate enzymes (3) their expression profiles are unique. We have isolated 13 tobacco CaM genes (NtCaM1-13) classified into three isoforms (NtCaM1 / NtCaM3 / NtCaM13). To study their functions and specificity in defense response against pathogens in tobacco, we analyzed their transcriptional activation, and found that transcripts of genes encoding NtCaM1 and NtCaM13 isoforms accumulated during hypersensitive response in Tobacco mosaic virus (TMV)-infected tobacco leaves containing the N resistance gene. Transgenic tobacco with reduced expression of NtCaM1 and NtCaM13 were respectively obtained through an RNAi strategy. Using these plants will report the roles of NtCaM isoforms on defense signals.
