| The plant growth and development were greatly affected by abiotic stresses, such as high or low temperature, drought and salinity, and resulted in significant reductions in crop yields and quality. Research on the functions of stress related genes in plant can provide theoretical basis for targeted genetic engineering of high stress tolerant crops. Plant K+efficiency can be genetically controlled, and diverse plant species have different K+efficiency. High K+efficiency is a target in genetic improvement of crop quality. The objective of this research is to characterize the functions of Arabidopsis UNC-93in stress tolerance, potassium transport and plant growth. The main results are as follows:1. A total of11highly heat responsive genes were screened from rice microarray data and19mutants of their homologous genes in Arabidopsis were obtained from ABRC. A total of11homozygous lines were identified by PCR and RT-PCR.2. The mutant unc-93-1and unc-93-2showed significantly decreased tolerance to high temperature, salt and osmotic stress among the11Arabidopsis mutants screened. The unc-93-2showed dwarf and later anthesis, while unc-93-1had less significant difference in plant type compared with wild type (WT) than that of unc-93-2. A truncate transcript of3’ end of UNC-93(behind the site of T-DNA) was detected in unc-93-1by RT-PCR analysis, but no any expression of UNC-93was detected in unc-93-2.3. UN-93is a K+channel regulatory protein. UNC-93is a membrane protein with10transmembrane helices. Transient expression assay located UNC-93at the plasma membrane in onion epidermal cells. The expression of UNC-93was induced by high temperature, salt, osmotic and abscisic acid (ABA) treatments. But there was no response to low temperature. Although the transcript of UNC-93could be detected in almost all tissues, it was higher in root and seedling. The activities of GUS were higher in root, seedling and vein by GUS assay in UNC-93promoter driven GUS report gene transgenic plants.4. The overexpression vectors of full or partial cDNA of UNC-93were constructed, and were separately transformed into WT (Col-0), unc-93-1or unc-93-2.5. The mutant unc-93-1and unc-93-2greatly decreased stress tolerance to high temperature, salt, drought, osmotic and ABA compared with WT. Overexpression of UNC-93significantly improved to salt and drought tolerance. No significant difference was observed between unc-93-1, unc-93-2UNC-93-overexpressing plants and WT under low temperature treatment. The expression levels of main stress related genes were significantly decreased in mutants but were upgraded in WVC-93-overexpressing plant. The expression levels of ABA-responsive genes, such as ABI1, ABI2, MYB2, SnKR2.6, had significantly differences among mutants, WVC-93-overexpressing plants and WT. Seed germination of unc-93-2and WVC-93-overexpressing line were greatly inhibited compared with WT under high temperature, salt, osmotic and ABA treatments, while unc-93-1mutant decreased sensitivity to these stresses compared with WT.6. Compared with WT, the K+contents in shoots of unc-93-1and unc-93-2were significantly decreased, WVC-93-overexpressing line had much higher K+contents under low K+concentration, but there were no obvious differences between WVC-93-overexpressing line and WT under normal K+concentration. There were no detectable changes of the K+contents in roots of unc-93-1, unc-93-2, WVC-93-overexpressing line and WT. Under normal condition, compared with WT, the growth and development of unc-93-2was inhibited, and the growth of unc-93-1was delayed, while WVC-93-overexpressing plants showed higher shoots and more roots. Under low potassium condition, compared with WT and WVC-93-overexpressing plants, the growth of unc-93-1and unc-93-2were inhibited more gravely and etiolation. The unc-93-1and unc-93-2showed brown cotyledons, curled principal roots and more lateral roots after seeds germination under low K+and NH4+concentration.7. The genetic complement assay showed that overexpression full cDNA of UNC-93can resume the tolerance to salt and osmotic stresses in unc-93-1and unc-93-2. The dwarf phenotype of unc-93-2returned to normal. When the overexpression vector of partial cDNA of UNC-93was transformed into unc-93-2, the dwarf phenotype of unc-93-2also returned to a certain extent. |
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