Expression of a subset of the Arabidopsis Cys(2)/His(2)-type zinc-finger protein gene family under water stress

The genes encoding Cys(2)/His(2)-type zinc-finger proteins constitute a lar ge family in higher plants. To elucidate the functional roles of these type s of protein, four different members of the gene family were cloned from Ar abidopsis by PCR-aided methods. One was identical to the already reported g ene STZ/ZAT10 and three were as yet unidentified genes, then designated AZF 1 (Arabidopsis zinc-finger protein 1), AZF2 and AZF3. The AZF- and STZ-enco ded proteins contain two canonical Cys(2)/His(2)-type zinc-finger motifs, s eparated by a long spacer. Three conserved regions, named B-box, L-box, and DNL-box, were also recognized outside the zinc-linger motifs, as in other members of the two-fingered Cys(2)/His(2)-type zinc-finger protein family. These four genes were positioned on the same branch of a phylogenetic tree constructed based on the zinc-ringer motif sequences, suggesting their stru ctural and functional relationship. RNA blot analysis showed that all four genes were mainly expressed in roots and at different levels in other organ s. Expression of the four genes responded to water stress. High-salt treatm ent resulted in elevated levels of expression of all of these genes. Low-te mperature treatment increased the expression levels of AZF1, AZF3, and STZ but not AZF2. Only AZF2 expression was strongly induced by ABA treatment, w here the time course of the induction was similar to that caused by high sa linity. In situ localization showed that AZF2 mRNA accumulated in the elong ation zone of the roots under the salt-stress condition. These results sugg est that AZF1, AZF2, AZF3, and STZ are all involved in the water-stress res ponse in an ABA-dependent or -independent pathway to regulate downstream ge nes. (C) 2000 Elsevier Science B.V. All rights reserved.