Increased expression of two cDNAs encoding metallothionein‐like proteins during growth of Cicer arietinum epicotyls

Abstract

The present study was undertaken to identify and characterize clones whose expres­sion increase during Cicer arietinum epicotyl growth. Two cDNAs encoding two different plant metallothionein (MT)-like proteins have been isolated from a cDNA library from epicotyls of Cicer arietinum L. cv. Castellana. The CanMT-1 deduced protein appears to have the typical structure of type I MT where ali Cys residues are in Cys-X-Cys motifs, while the CanMT-2 has the typical structure of type 2 MT having Cys-Cys and Cys-X-X-Cys motifs within the N-terminal domain. Both chickpea CanMTs are up-regulated during epicotyl growth, showing increased ex­pression in mature tissues, mostly CanMT-1, which is undetectable in young epi­cotyls. Accordingly, stem of chickpea plants displayed the highest leve! of CanMT-1 expression in the basal internode, with reduced growth, decreasing towards the apex. Osmotic stress by PEG, which inhibited growth, and ABA treatment induced the expression of MT-like genes, which points to a relationship between chickpea MTs and ABA-mediated stress response. Unlike CanMT-2, CanMT-1 is induced in chickpea epicotyls by cadmium indicating a different function for both clones. We conclude that these MT-like proteins, in particular CanMT-1, are regulated by the developmental stage and may participate in cell maturation process