Overexpression of the receptor-like protein kinase genes AtRPK1 and OsRPK1 reduces the salt tolerance of Arabidopsis thaliana.

AtRPK1 (AT1G69270) is a leucine-rich repeat receptor-like protein kinase (LRR-RLK) gene in Arabidopsis thaliana. The rice gene Os07g0602700 (OsRPK1) is the homolog of AtRPK1. AtRPK1 and OsRPK1 were overexpressed and the expression of AtRPK1 was inhibited by RNAi in A. thaliana. The functional results showed that the degrees of salt tolerance of the 35S:RPK1 A. thaliana plants were significantly lower than that of the control plants. The AtRPK1-RNAi A. thaliana plants exhibited higher salt tolerance than the wild-type plants (Col). The subcellular localisation results showed that the RPK1 proteins were mainly distributed on the cell membrane and that the overexpressed AtRPK1 proteins exhibited a significantly clustered distribution. The physiological analyses revealed that the overexpression of the RPK1 genes increased the membrane permeability in the transgenic A. thaliana plants. In response to salt stress, these plants exhibited an increased Na(+) flux into the cell, which caused greater damage to the cell. The real-time quantitative PCR analysis showed that the expression of the P5CS1 gene was inhibited and the SOS signalling pathway was blocked in the 35S:AtRPK1 A. thaliana plants. These effects at least partially contribute to the salt-sensitive phenotype of the 35S:RPK1 plants.

Overexpression of TaSTRG gene improves salt and drought tolerance in rice.

High salt and drought are the main factors affecting agricultural production. Thus, cloning stress-tolerance-related genes and identifying their functions are essential to enhancing crop tolerance to stresses. In this study, a salt-induced unknown wheat (Triticum aestivum L.) gene was identified and cloned according to microarray analysis of salt-tolerant wheat mutant RH8706-49 under salt stress. The gene was named Triticum aestivum salt tolerance-related gene (TaSTRG) and submitted to Genbank (Accession number: EF599631). TaSTRG expression in wheat is induced by multiple stresses including salt, polyethylene glycol (PEG), abscisic acid (ABA), and cold. Transgenic rice plants overexpressing TaSTRG gene showed higher salt and drought tolerance than the control. Under salt stress, the transgenic rice had a lower intracellular Na(+)/K(+) ratio than the control. Under salt and PEG treatments, these TaSTRG overexpressing rice plants had higher survival rate, fresh weight and chlorophyll content, accumulated higher proline and soluble sugar contents, and had significantly higher expression levels of putative proline synthetase and transporter genes than the control plants. These results indicate that the wheat TaSTRG gene could enhance plant tolerance to multiple types of stresses.

Cloning and functional analysis of wheat V-H+-ATPase subunit genes.

The root microsomal proteomes of salt-tolerant and salt-sensitive wheat lines under salt stress were analyzed by two-dimensional electrophoresis and mass spectrum. A wheat V-H(+)-ATPase E subunit protein was obtained whose expression was enhanced by salt stress. In silicon cloning identified the full-length cDNA sequences of nine subunits and partial cDNA sequences of two subunits of wheat V-H(+)-ATPase. The expression profiles of these V-H(+)-ATPase subunits in roots and leaves of both salt-tolerant and salt-sensitive wheat lines under salt and abscisic acid (ABA) stress were analyzed. The results indicate that the coordinated enhancement of the expression of V-H(+)-ATPase subunits under salt and ABA stress is an important factor determining improved salt tolerance in wheat. The expression of these subunits was tissue-specific. Overexpression of the E subunit by transgenic Arabidopsis thaliana was able to enhance seed germination, root growth and adult seedling growth under salt stress.

[Introduce Tagsk1 into salt-sensitive callus to improve the capacity of salt-tolerance by micropartical bombardment].

The Tagsk1 (Triticum asetium L. glycogen synthase kinase 1) gene derived from the genome of wheat salt-tolerance mutant RH8706-49 was cloned by PCR. The special primers designed according to full length cDNA sequence of Tagsk1 (AF525086). A binary expression vector pBI121-gsk1 containing Gus and Tagsk1 was constructed. And pBI121-gsk1 was introduced into the callus induced from mature embryos of salt-sensitive wheat H8706-34 and cv. China Spring by particle bombardment. The transformed callus were screened by Kanamycin and 0.5% NaCl. The salt-tolerance callus were obtained, which showed higher ability of salt-tolerance and could diffirentiate roots and buds on the medium containing 0.5% NaCl.

[Proteomic analysis of the salt tolerance mutant of wheat under salt stress].

Two dimensional electrophoresis was used to analyse the proteome of the salt-tolerant mutant of wheat (RH8706-49) and the salt-sensitive mutant of wheat (H8706-34) which had been treated by 1% NaCl for 72 hours. After being analysed by MALDI-TOF-MS and Mascot software, the qualitative and quantitative differences were identified between the two materials for five candidate proteins: H+-transporting two-sector ATPase, glutamine synthetase 2 precursor, putative 33 kD oxygen evolving protein of photosystem II and ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit. These five proteins are all belong to chloroplast proteins. They are likely to play a crucial role in keeping the function of the chloroplast and the whole cells when the plant was under salt-stress.