| SGT1and RAR1play a very important role in plant disease resistance signal transduction. SGT1is an essential regulator in the cell cycle, required for the early stage in plant growth and development. RAR1is an early convergence point in a signaling pathway. SGT1-RAR1complex interacts with two COP9signalsome, indicates an interlinkage between disease resistance and ubiquitination.In this paper, we cloned the cDNA of SGT1and RAR1in papaya by RT-PCR successfully, then constructed reorganized over-expression vectors:pBI121-SGT1-RAR1. Generated the transgenic plants over-expression in the Arabidopsis ecotype Columbia (Col-0) using the floral dipping method, identified the function of SGT1and RAR1in Arabidopsis, with the four transgenic plants:pBI121-SGT1-GUS、pBI21-SGT1、 pBI121-RAR1-GUS, pBI121-RAR1. The main results of this study were as follows:1. Compared the transgenic Arabidopsis T2progeny with ecotype Col-0, we found that distinction showed in taproot length, lateral root number, bolting period and floral axis length. The results indicated that SGT1in papaya is required for the early stage in Arabidopsis growth and development.2. The rate of seed germination, and the extent of root elongation were observed and recorded, when the plants in response to salt stress and osmotic stress. Seeds of the three RAR1over-expression transgenic lines (pBI121-SGT1-RAR1、 pBI121-RAR1-GUS、pBI121-RAR1) showed95%,76%and88%germination on mannitol-containing media, which is much higher than the germination of SGT1over-expression transgenic plants. The results indicated that over-expression of RAR1enhanced Arabidopsis seed germination under osmotic or salt stress.Determined the effects of SGT1、RAR1over-expression on seedling development. Root growth of pBI121-RAR1plants was more sensitive to osmotic stress compared to the other five plants, while over-expression of SGT1plants was less sensitive to salt stress compared to RAR1over-expression and wild-type plants. Thus, elevated expression of SGT1is involved in controlling osmotic and salt stress tolerance in Arabidopsis seedlings development.3. Detached leaves were tested to oxidative stress with pBI121-SGT1、and pBI121-RAR1transgenic plants. After48h of oxidative treatment, wild-type suffered severe browning and desiccation damage while the two transgenic Arabidopsis plants showed delayed browning and desiccation damage. The results showed that leaves of pBI121-SGT1and pBI121-RAR1transgenic plants had enhanced tolerance to oxidative stress.4. Arabidopsis leaves were infiltrated with the hypha of Ep-1PNA367. Disease spots extended the whole Col-0leaves, but not appearance at the whole leaves of transgenic Arabidopsis after39h infiltration. Disease spots appeared on the Col-0Arabidopsis leaves, meanwhile disappearance on the other four Arabidopsis leaves after15h infiltration. These results indicated that SGT1and RAR1are required for the disease resistance in Arabidopsis leaves.To further investigate whether the two genes are crucial for disease resistance, we did the statistics of disease spot area. The disease spot of pBI121-SGT1was smaller than the other Arabidopsis leaves after15h infiltration, and the disease spot of pBI121-RAR1-GUS was obviously bigger than the others after21h infiltration, until the disease spot extended the whole leaf. These results support our findings that the SGT1and RAR1are required for the disease resistance in Arabidopsis leaves.5. Definited the role of SGT1and RAR1in R gene-mediated resistance immune response pathways, changes in genome-wild associated with SGT1and RAR1over-expression was studied. Expression of four related resistance genes including EDS1、NDR1、RPP5and LOX2was monitored, different folds expressed in Col-0and transgenic Arabidopsis. Provide new evidence for interaction mechanisms between SGT1、RAR1and related R genes. |
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