TANDEM ZINC-FINGER PROTEINS ARE INVOLVED IN SEED GERMINATION AND ABIOTIC STRESS RESPONSE IN ARABIDOPSIS AND DURUM WHEAT

CCCH zinc finger domain consists of a sequence with three cysteines and one histidine residues with strictly defined spacing: C-X4-15-C-X4-6-C-X3-H. As in animals, even in plants this domain has been found in some RNA-binding proteins involved in several important biological processes. A genome-wide analysis has identified 68 and 67 CCCH family genes in Arabidopsis and rice, respectively, these genes are divided in several sub-family, among them the Tandem Zinc Finger (TZF) gene subfamily contains a unique TZF motif that can only be found in plants, and its members are involved in stress response. TZF genes are represented throughout the evolutionary scale, from algae to higher plants. The phylogenetic analysis revealed that zinc-finger domain is strongly conserved from algae to higher plants, suggesting that these domains have a primary importance for the molecular function of these proteins. Our attention was focused on a Triticum durum TZF protein, TdTZF1-A, and its homeologous gene, TdTZF1-B. Full length sequences of TdTZF1-A (characterized as responsive to cold and dehydration stresses) and TdTZF1-B genes were obtained from the Creso variety and they were found to correspond to homoelogous genes positioned on chromosomes 3A and 3B respectively. Among Arabidopsis TZF genes, AtTZF3 is the putative ortholog of TdTZF1-A, and to carryout a functional study we created under- and over-expression mutants for this gene. A deep phenotipic evaluation of the germination process in presence of ABA was performed. AtTZF3 silenced lines showed a better germination capacity in ABA treatments than wilde-type. Conversely, overexpressing lines have a greater difficulty to germinate in the same conditions. Similar results are obtained under salt stress. These data suggest that AtTZF3 is a negative regulator of seed germination. Expression analysis under stress conditions and germination suggests the involvement of TdTZF1-A and TdTZF1-B in the regulation of seed germination in durum wheat.