| High salinity affects crop yield and quality.Rice,as one of the staple food crops for more than half of the world’s population,is a salt-sensitive crop at different growth stages.It is of paramount significance to investigate the salinity tolerance of rice and further investigate the regulation factors and mechanisms involved in the cascade of salt stress response of rice.Dof family genes play an important role in abiotic stresses such as drought,high salinity and low temperature in a variety of crops,but these functions have not been comprehensively undermined in rice.In present study,we employed OsDof15-related transgenic materials created to analyze the role of Dof family proteins in response to salt stress in rice.On the other hand,as a semi-aquatic crop,coleoptile of rice plays an integral role in the process of seedling unearthing and tolerance to water flooding.In order to further explore the key factors that govern the growth,we screened the mutant bank of rice and acquired a coleoptile defective mutant.The results obtained are as follows:1.Our result demonstrated that expression level of OsDof15 gene was detected under various abiotic stresses and hormones.Obviously,the expression of OsDof15 can be induced rapidly under salt stress.The tolerance of OsDof15 was further investigated under salt stress.Surprisingly,it was revealed that mutant seedlings depicted lower salt tolerance as compared to wild type,however,the salt tolerance of over-expression seedlings was higher,which presented that OsDof15 is involved in regulation of salt tolerance in rice.2.The AsA content of OsDof15-related transgenic seedlings was detected,and it was observed that AsA content was less in osdof15 mutant plants compared to wild-type,while the over-expression seedlings showed higher AsA concentration,signifying that the AsA content in rice was regulated by OsDofl 5.In order to investigate whether AsA plays a crucial role in positive regulation of OsDof15 in salt tolerance of rice,we revealed that the salt tolerance of osdo.f15 mutants could be restored to same extent as in wild-type by supplementing AsA at the same time of salt treatment.This designated that OsDofl 5 has the potential to enhance the salt tolerance by positively upregulating the content of AsA in rice.3.Previously,our laboratory has proven that OsDof15 negatively regulates the synthesis of ethylene.Therefore,we tried to further explore the association between ethylene and salt tolerance in rice.Ethylene receptor mutants and signal mutants(two each)were utilized to study the salt tolerance.The results demonstrated that ethylene negatively regulate the salt tolerance of rice.Furthermore,in order to study the role of AsA in ethylene negative regulation of salt tolerance in rice,we observed the phenotypes of ethylene-related mutants could be were able to recover to the level of the corresponding wild-type when we supplemented the AsA exogenously at the same interval of salt treatment.Therefore ethylene by negatively regulation AsA content to enhance the salt resistance of rice in vivo.These findings suggest that OsDof15 might improve the salt tolerance by negatively regulating ethylene synthesis and then regulating the AsA content,which enrich the molecular mechanism of Dof proteins family in regulation of salt tolerance in rice.4.By comprehensive screening of mutant library of rice,a series of coleoptile defective mutants were acquired.A mutant,short coleoptile 1(scpl)contained significantly shorter coleoptile than wild type.Results established that both the expression of ethylene synthesis and ethylene release in scpl were lower as compared to its counterpart.5.Additionally,the agronomic characters of scpl were also studied.Astonishingly,it was established that as compared to wild type,scpl illustrates the phenotype of dwarfing,short spike and small grains.Under stress conditions(salt and drought treatments),scpl depicted higher salt tolerance and drought resistance.6.The SCP1 gene was mapped to the 32.01 kb interval on chromosome 5 by map-based cloning,and there were five functional genes in the region.By using sequencing tools,it was established that sequences of one of the genes,OsRGAl,was deleted into a large segment in the mutant.Moreover,scpl posses similar short coleoptile and inverse-resistance to the allelic mutant dl of OsRGA1 that has been reported previously,designating that scpl was an allelic mutant of OsRGA1.In conclusion,our study led a deep foundation to explore the molecular mechanisms of OsRGAl and demonstrated it as beneficial to augment the regulation of ethylene synthesis in rice. |
