Overexpression of a TFIIIA-type zinc finger protein gene ZFP252 enhances drought and salt tolerance in rice (Oryza sativa L.)

We previously identified a salt and drought stress-responsive TFIIIA-type zinc finger protein gene ZFP252 from rice. Here we report the functional analysis of ZFP252 using gain- and loss-of-function strategies. We found that overexpression of ZFP252 in rice increased the amount of free proline and soluble sugars, elevated the expression of stress defense genes and enhanced rice tolerance to salt and drought stresses, as compared with ZFP252 antisense and non-transgenic plants. Our findings suggest that ZFP252 plays an important role in rice response to salt and drought stresses and is useful in engineering crop plants with enhanced tolerance to salt and drought stresses.     

A novel rice C2H2-type zinc finger protein lacking DLN-box/EAR-motif plays a role in salt tolerance

A cDNA for the gene ZFP182, encoding a C2H2-type zinc finger protein, was cloned from rice by RT-PCR. ZFP182 codes an 18.2 kDa protein with two C2H2-type zinc finger motifs, one nuclear localization signal and one Leu-rich domain. The DLN-box/EAR-motif, which exists in most of plant C2H2-type zinc finger proteins, does not exist in ZFP182. The expression analysis showed that ZFP182 gene was constitutively expressed in leaves, culms, roots and spikes at the adult rice plants, and markedly induced in the seedlings by cold (4 °C), 150 mM NaCl and 0.1 mM ABA treatments. The approximate 1.4 kb promoter region of ZFP182 gene was fused into GUS reporter gene and transformed into tobacco. The histochemical analysis revealed that GUS expression could not be detected in transformed tobacco seedlings under normal conditions, but strongly observed in tobacco leaf discs and the vascular tissue of roots treated with NaCl or KCl. Expression of ZFP182 in transgenic tobacco and overexpression in rice increased plant tolerance to salt stress. These results demonstrated that ZFP182 might be involved in plant responses to salt stress.     

Overexpression of a wheat MYB transcription factor gene, TaMYB56-B, enhances tolerances to freezing and salt stresses in transgenic Arabidopsis

The MYB proteins play central roles in the stress response in plants. Our previous works identified a cold stress-related gene, TaMYB56, which encodes a MYB protein in wheat. In this study, we isolated the sequences of TaMYB56 genes, and mapped them to the wheat chromosomes 3B and 3D. The expression levels of TaMYB56-B and TaMYB56-D were strongly induced by cold stress, but slightly induced by salt stress in wheat. The detailed characterization of the Arabidopsis transgenic plants that overexpress TaMYB56-B revealed that TaMYB56-B is possibly involved in the responses of plant to freezing and salt stresses. The expression of some cold stress-responsive genes, such as DREB1A/CBF3 and COR15a, were found to be elevated in the TaMYB56-B-overexpressing Arabidopsis plants compared to wild-type. These results indicate that TaMYB56-B may act as a regulator in plant stress response.     

The conserved Ala37 in the ERF/AP2 domain is essential for binding with the DRE element and the GCC box

Four AP2/EREBP genes encoding putative ethylene-responsive element binding factor (ERF)/AP2 domains were cloned from Brassica napus, and these genes could be induced by low temperature, ethylene, drought, high salinity, abscisic acid and jasmonate treatments. These four genes, named BnDREBIII-1 to BnDREBIII-4, were highly homologous and the 37th amino acid was the only difference among their ERF/AP2 domains. BnDREBIII-1 was demonstrated to be able to bind to both dehydration-responsive element and the GCC box and transactivate the expression of downstream genes, while BnDREBIII-4 could bind neither. Further results suggested that Ala37 might play a crucial role in the DNA binding or the stability of the ERF/AP2 domain.     

Differential expression profiles of poplar MAP kinase kinases in response to abiotic stresses and plant hormones,and overexpression of PtMKK4 improves the drought tolerance of poplar

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules that play essential roles in plant growth, development and stress response. MAPK kinases (MAPKKs), which link MAPKs and MAPKK kinases (MAPKKKs), are integral in mediating various stress responses in plants. However, to date few data about the roles of poplar MAPKKs in stress signal transduction are available. In this study, we performed a systemic analysis of poplar MAPKK gene family expression profiles in response to several abiotic stresses and stress-associated hormones. Furthermore, Populus trichocarpa MAPKK4 (PtMKK4) was chosen for functional characterization. Transgenic analysis showed that overexpression of the PtMKK4 gene remarkably enhanced drought stress tolerance in the transgenic poplar plants. The PtMKK4-overexpressing plants also exhibited much lower levels of H₂O₂ and higher antioxidant enzyme activity after exposure to drought stress compared to the wide type lines. Besides, some drought marker genes including PtP5CS, PtSUS3, PtLTP3 and PtDREB8 exhibited higher expression levels in the transgenic lines than in the wide type under drought conditions. This study provided valuable information for understanding the putative functions of poplar MAPKKs involved in important signaling pathways under different stress conditions.