Function Analysis Of Salt Tolerance Mediated By GbSRP1 In Cotton

Plants face several environmental stresses simultaneously.It is reported that soil salinization is becoming aggravated,which has seriously been one of the major threats.With salt stress,plants have evolved various mechanisms to ensure their self-existence and sustainable growth.When the salt concentration in the soil increases,the yield of the crop will decrease.In view of the great harm of soil salinization to agricultural production,it has become the most important task to study the salt tolerance mechanism and breed salt-tolerant crop varieties.Although recent reports on the salt response mechanism are increasing,there are few reports on cotton.In the previous study,we found that GbSRP1?Gossypium barbadense Salt Response Protein 1?could be induced by salt in cotton.Based on the previous research,we do further research on the salt tolerance mechanism of GbSRP1 in this study.There is no difference of the K⁺and Na⁺content,as well as K⁺/Na⁺ratio,in TRV:00 and TRV:SRP1 plants without NaCl treatment.However,the Na⁺content and K⁺/Na⁺ratio of TRV:SRP1 plants were significantly higher than that of TRV:00 plants with NaCl treatment.There was no difference of K⁺content with NaCl treatment.Meanwhile,the result of Na⁺staining showed that Na⁺content in the TRV:SRP1 plants roots was higher than that of TRV:00 plants with NaCl treatment.These results indicated that the Na⁺transportation ability decreased while silengcing GbSRP1 gene in cotton.Na⁺is accumulated in TRV:SRP1,resulting in toxicity to cells with NaCl treatment and reducing the tolerance to salt.The function of GbSRP1 was further studied by overexpressing in the ion-deficient yeast mutant ydr.The growth status of pYES2-GbSRP1-1 and pYES2-GbSRP1-2 yeast strains which overexpressed GbSRP1was better than ydr and pYES2 strains in under the medium containing NaCl,which illustrated that salt tolerance of yeast strains containing pYES2-GbSRP1-1 or pYES2-GbSRP1-2 is higher than ydr and pYES2strains.This indicated that GbSRP1 could enhance the salt tolerance of the ion-deficient yeast mutant.In order to study the salt tolerance of GbSRP1 in cotton,we constructed the overexpression vector and transferred the vector into cotton for further exploration.A total of 8 positive transgenic lines and 3negative transgenic lines were obtained.The expression of GbSRP1 in the overexpressed plants was significantly increased.After salt treatment,the growth status of the overexpression plants was better than that of the wild type and negative plants.The wilted rate of overexpression plants was much lower than that of wild type and negative plants.The physiological data showed that the content of MDA and H₂O₂ of the overexpression plant were lower than that of wild type with NaCl treatment.The leaf disks of wild type plants with NaCl treatment became brown,at the same time the disks of overexpression plants remained green.There was no difference about the chlorophyll content of wild type and overexpression plant without NaCl treatment.The chlorophyll content of overexpression plant disks was higher than that in wild type with NaCl treatment.These results further indicated that GbSRP1 could improve the salt tolerance of cotton.In order to further analyze the mechanism of salt tolerance,we constructed a bait vector to screen proteins interacting with GbSRP1.Some candidate proteins were screened from yeast library interacting with GbSRP1.The interaction of candidate proteins?IP-2,IP-4 and IP-5?with GbSRP1 was further proved by BiFC experiments.In conclusion,GbSRP1 is involved in the salt tolerance of cotton.The GbSRP1 gene can improve the salt tolerance of transgenic yeast and cotton.We also screen the interaction proteins with GbSRP1preliminarily.It provides not only new insights for further study on the salt response mechanism of GbSRP1,but also foundations for improving the breeding of salt tolerant varieties.