Novel potato C2H2‐type zinc finger protein gene,StZFP1, which responds to biotic and abiotic stress,plays a role in salt tolerance

Many TFIIIA‐type zinc finger proteins (ZFPs) play important roles in stress responses in plants. In the present study, a novel zinc finger protein gene, StZFP1, was cloned from potato. StZFP1 is a typical TFIIIA‐type two‐finger zinc finger gene with one B‐box domain, one L‐box domain and a DLN‐box/EAR motif. The StZFP1 genes belong to a small gene family with an estimated copy number of four or five, located on chromosome I. StZFP1 is constitutively expressed in leaves, stems, roots, tubers and flowers of adult plants. Expression of StZFP1 can be induced by salt, dehydration and exogenously applied ABA. StZFP1 expression is also responsive to infection by the late blight pathogen Phytophthora infestans. Transient expression analysis of StZFP1:GFP fusion protein revealed that StZFP1 is preferentially localised in the nucleus. Ectopic expression of StZFP1, driven by the Arabidopsis rd29A promoter in transgenic tobacco, increased plant tolerance to salt stress. These results demonstrate that StZFP1 might be involved in potato responses to salt and dehydration stresses through an ABA‐dependent pathway.     

Functional Characterization of Maize C<Subscript>2</Subscript>H<Subscript>2</Subscript> Zinc-Finger Gene Family

Plant C2H2-type zinc finger proteins (ZFPs) play essential roles in developmental control and stress responses. The whole complement of ZFP genes has been identified in Arabidopsis and rice, while the genome-scale identification and functional analysis of maize ZFPs is not yet reported. Hence, we performed a comprehensive analysis, including gene structure, chromosome location, duplicated event, selective pressure, phylogeny, gene ontology annotation, and expression profiling under developmental stages and abiotic stresses. Phylogenetic analyses suggested that the ZmZFP gene family can be grouped into three classes (A, B, and C). The analysis of differential gene expression in different developmental stages and stress treatments (drought, salt, and cold) was conducted based on microarray and RNA-seq data. A total of 99.05 % (209 genes) of the total ZmZFP genes (211 genes) were detected in 60 different tissues in microarray data. Under drought stress, 13 differentially expressed genes were found in leaf, of which 7 and 6 genes were up-regulated and down-regulated, respectively. For salt stress, crown root (CR), primary root (PR) and seed root (SR) each had one significantly elevated gene, while 2, 1, and 7 genes were obviously down-regulated in CR, PR and SR, respectively. Additionally, 8 and 3 genes were significantly up-regulated and down-regulated, respectively, in the cold-tolerant line ETH-DH7. This study will lay the foundation for understanding the roles of ZFPs in maize growth and stress resistance, contributing to the molecular breeding of maize for food.     

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 large family in higher plants. To elucidate the functional roles of these types of protein, four different members of the gene family were cloned from Arabidopsis by PCR-aided methods. One was identical to the already reported gene STZ/ZAT10 and three were as yet unidentified genes, then designated AZF1 (Arabidopsis zinc-finger protein 1), AZF2 and AZF3. The AZF- and STZ-encoded proteins contain two canonical Cys(2)/His(2)-type zinc-finger motifs, separated by a long spacer. Three conserved regions, named B-box, L-box, and DNL-box, were also recognized outside the zinc-finger 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-finger motif sequences, suggesting their structural and functional relationship. RNA blot analysis showed that all four genes were mainly expressed in roots and at different levels in other organs. Expression of the four genes responded to water stress. High-salt treatment resulted in elevated levels of expression of all of these genes. Low-temperature treatment increased the expression levels of AZF1, AZF3, and STZ, but not AZF2. Only AZF2 expression was strongly induced by ABA treatment, where the time course of the induction was similar to that caused by high salinity. In situ localization showed that AZF2 mRNA accumulated in the elongation zone of the roots under the salt-stress condition. These results suggest that AZF1, AZF2, AZF3, and STZ are all involved in the water-stress response in an ABA-dependent or -independent pathway to regulate downstream genes.     

小拟南芥ApZFP基因异源超表达促进拟南芥开花并提高耐逆性

锌指蛋白(ZFP)是一类重要的转录因子, 广泛参与植物的生长发育和非生物胁迫应答。新疆小拟南芥(Arabidopsispumila)又名无苞芥, 是十字花科短命植物, 具有高光效、繁殖力强和适应干旱等生物学特征, 而且比模式植物拟南芥(A.thaliana)更耐高盐胁迫。将前期克隆的小拟南芥锌指蛋白基因ApZFP通过花滴法转化到哥伦比亚生态型拟南芥(Col-0)中,获得了独立表达的转基因株系。表型观察发现, 过量表达ApZFP基因可促使拟南芥在长短日照下均提前开花。实时荧光定量PCR结果显示, 转基因拟南芥株系中, 光周期途径中的CO基因和年龄途径中的SPL基因表达上调; 春化、环境温度和自主途径中的FLC基因表达下调; 编码成花素的基因FT及下游开花相关基因AP1和LFY的表达量均升高。进一步通过盐、干旱和ABA胁迫处理ApZFP转基因株系的种子和幼苗, 发现在胁迫处理下, 与对照相比, 转基因拟南芥种子萌发率较高, 幼苗主根较长。因此推测, ApZFP在植物发育过程中具有多种功能, 可能既参与植物的开花转变过程, 又同其它植物的锌指蛋白基因一样, 参与植物的耐逆过程。     

Cold shock domain proteins in the extremophyte Thellungiella salsuginea (salt cress): gene structure and differential response to cold

Four genes encoding cold shock domain (CSD) proteins have been identified in salt cress [Thellungiella salsuginea (halophila), an extremophyte currently recognized as a promising model for studying stress tolerance]. The deduced proteins prove highly homologous to those of Arabidopsis thaliana (up to 95% identity) and are accordingly enumerated TsCSDP1-TsCSDP4; after the N-proximal conserved CSD, they have respectively 6, 2, 7, and 2 zinc finger motifs evenly spaced by Gly-rich stretches. Much lower similarity (approximately 45%) is observed in the regions upstream of TATA-box promoters of TsCSDP1 vs. AtCSP1, with numerous distinctions in the sets of identifiable cis-regulatory elements. Plasmid expression of sCSDP1 rescues a cold-sensitive cup-lacking mutant of Escherichia coli, confirming that the protein is functional. In leaves of salt cress plants under normal conditions, the mRNA levels for the four TsCSDPs relate as 10: 27: 1: 31. Chilling to 4 degrees C markedly alters the gene expression; the 4-day dynamics are different for all four genes and quite dissimilar from those reported for their Arabidopsis homologues under comparable conditions. Thus, the much greater cold hardiness of Thellungiella vs. Arabidopsis cannot be explained by structural distinctions of its CSDPs, but rather may be due to expedient regulation of their expression at low temperature.     

The CCCH-type zinc finger proteins AtSZF1 and AtSZF2 regulate salt stress responses in Arabidopsis

The molecular mechanism governing the response of plants to salinity stress, one of the most significant limiting factors for agriculture worldwide, has just started to be revealed. Here, we report AtSZF1 and AtSZF2, two closely related CCCH-type zinc finger proteins, involved in salt stress responses in Arabidopsis. The expression of AtSZF1 and AtSZF2 is quickly and transiently induced by NaCl treatment. Mutants disrupted in the expression of AtSZF1 or AtSZF2 exhibit increased expression of a group of salt stress-responsive genes in response to high salt. Significantly, the atszf1-1/atszf2-1 double mutant displays more sensitive responses to salt stress than the atszf1-1 or atszf2-1 single mutants and wild-type plants. On the other hand, transgenic plants overexpressing AtSZF1 show reduced induction of salt stress-responsive genes and are more tolerant to salt stress. We also showed that AtSZF1 is localized in the nucleus. Taken together, these results demonstrated that AtSZF1 and AtSZF2 negatively regulate the expression of salt-responsive genes and play important roles in modulating the tolerance of Arabidopsis plants to salt stress.