Functional Analysis Of Maize Stress Response Genes ZmSnRK2.11,ZmCBL9and ZmCBL10

Sucrose non-fermenting-1related protein kinase2(SnRK2) is a unique family of protein kinases associated with abiotic stress signal transduction in plants. In our study, protein sequence analysis revealed that ZmSnRK2.11possesses the typical features of the SnRK2subfamily. Phylogenetic analysis showed ZmSnRK2.11clustered in the same clade as ZmSAPK4, SbSAPK4and TpSnRK2.11. In addition, the results showed that ZmSnRK2.11is up-regulated by high-salinity and dehydration treatment, and expressed mainly in maize mature leaves. A transient expression assay using onion epidermal cells revealed that ZmSnRK2.11-GFPfusion proteins are localized to both the nucleus and cytoplasm. Overexpressing-ZmSnRK2.11in Arabidopsis resulted in salt and drought sensitivity phenotypes that exhibited an increased rate of water loss, reduced relative water content, delayed stoma closure, accumulated less free proline content and increased malondialdehyde (MDA) content relative to the phenotypes observed in wild-type (WT) control. Furthermore, overexpression of ZmSnRK2.11up-regulated the expression of the genes ABll and ABI2and decreased the expression of DREB2A and P5CS1. Taken together, our results suggest that ZmSnRK2.11is a possible negative regulator involved in the salt and drought stress signal transduction pathway in plants.The calcineurin B-like protein (CBL) family, as a second messager, represents a unique group of calcium sensors in plants. In this study, we identified an AtCBL9homolog, ZmCBL9, from the maize genome. Tissue-specific expression of ZmCBL9shows higher transcript level in seedling leaves and mature leaves and roots. In addition, transcription level of ZmCBL9was induced by NaCl, mannitol, and glucose stress signals and abscisic acid (ABA) treatment in young seedlings. ZmCBL9can rescue the hypersensitive phenotype of cbl9mutant, and overexpression of ZmCBL9also can enhance tolerance to ABA, NaCl, mannitol and glucose stresses. Further analyses showed that ZmCBL9not only play as a negative regulator in ABA biosynthesis and signaling transduction, but also might up regulate the expression of AtABCG40. These results suggest ZmCBL9may involve in modulate ABA biosynthesis and signaling transduction. The results from the yeast two-hybrid assay indicated that ZmCBL9can interact with8ZmCIPKs, and ZmCBL9may involve in seed germation, phytohormone regulation and response to stress conditions by binding with these ZmCIPKs.Sequence analysis showed that ZmCBL10has a high sequence identity with AtCBL10and OsCBL9. Expression level of ZmCIBL10was higher in seedling roots and mature leaves, stem and roots Abiotic stresses, including NaCl and dehydration, strongly induced expression of ZmCBL10, however, the expression level of ZmCBL10was suppressed under low potassium stress. ZmCBL10-GFP fusion protein expressed in plasma membrane and pre-vacuolar membrane, and the transmember region in N treminal is essential for its membrane localization. In our study, ZmCBL10not only can rescue the hypersensitive phenotype of cb110mutant, but also can functionally complement the sos3mutant. Moreover, overexpression of ZmCBL10can enhance transgenic plants tolerance to NaCl stress, but decrease the tolerance to low potassium stress, which suggests ZmCBL10may also have important function in modulate Na+/K+homeostasis.