1、As a second messenger, Ca2+ plays major role in cold induced transduction via stimulus-specific increases in [Ca2+]cyt, which is called calcium signature.During this process, CAXs (Ca2+/H+ exchangers) play critical roles

2、.For the first time, putative Ca2+/H+ exchanger GhCAX3 and GhCAX1 genes from upland cotton (Gossypium hirsutum cv.'YZ-1) were isolated and characterized.GhCAX3 and GhCAX1 genes may act as a regulator in cotton responsive

3、 to abiotic stresses as it could be up-regulated by Ca2+, NaCl, ABA and cold stress.Similar to other CAXs, it was proved that GhCAX3 and GhCAX1 also had Ca2+ transport activity and the N-terminal regulatory region (NRR)t

4、hrough yeast complementation assay.Over-expression of GhCAX3 in tobacco showed less sensitivity to ABA during seed germination and seedling stages, but the phenotypic difference between wild type (WT) and transgenic plan

5、ts was more significant when the NRR was truncated.Furthermore, GhCAX3 conferred cold tolerance in yeast as well as tobacco seedlings based on the investigation at physiological and molecular level.However, transgenic pl

6、ant seeds showed more sensitivity to cold stress compared to WT during seed germination, especially when expressed in N-terminal truncated version.Finally, the extent of sensitivity in transgenic lines was more severe th

7、an that in WT line under sodium tungstate treatment (an ABA repressor), indicating ABA could alleviate cold sensitivity of GhCAX3 seeds, especially in short of its NRR.Meanwhile, we also found that overexpression of GhCA

8、X3 could enhance some cold and ABA responsive marker genes.Taken together, these results suggested that GhCAX3 played important roles in the cross-talk of ABA and cold signal transduction, and compared with full-length o

9、f GhCAX3, the absence of NRR could enhance the tolerance or sensitivity extent against stresses.Overexpression of GhCAX1 in tobacco also showed less sensitivity to ABA, Li+ and Mn2+ during seed germination and seedling d

10、evelopment.Under ABA treatment, transgenic plant seeds showed more tolerance compared to WT during seed germination, especially when expressed in N-terminal truncated version.GhCAX1 conferred enhanced tolerance of transg

11、enic tobacco plants to cold under chilling or freezing temperatures.GhCAX1 also showed tolerance to cold during seedling development, extent of tolerance was same both in N-terminal truncated form and full-length.Of spec

12、ial note, treatment of the transgenic tobacco plants with POD inhibitors elevated the H2O2 levels and greatly compromised their cold tolerance.In addition, transgenic tobacco showed more tolerant to oxidative stresses du

13、ring seed germination, seedling development and maturation.Taken together, these findings exhibit that GhCAX1 plays a pivotal role in cold tolerance, at least in part, by positively regulating POD-mediated reactive oxyge