盐胁迫下野菊离子的吸收转运情况及相关基因的表达分析

[Objective]The aim of this study was to elucidate the ion distribution and transport characteristics of various Chrysanthemum indicum strains with differing salt tolerate abilities under salt stress.Additionally,the study also aimed to investigate the changes in related genes.In order to gain a deeper understanding of the salt tolerance mechanism of Dendranthema indicum and provide a reference for the subsequent development and cultivation of new salt-tolerant varieties.[Method]The previously selected two high resistant strains(H1,H2),two middle resistant strains(M1,M2),and two low resistant strains(L1,L2)were used as experimental materials,and were subjected to salt stress treatment in Hoagland nutrient solution with 150mmol/L NaCl.The content of Na+ and K+ ions in the roots,stems,and leaves were measured,the K+/Na+ ratio in the roots,stems,and leaves,and the K+/Na+ selectivity ratio(SK+,Na+)in different parts of the strains were calculated.The effects of salt stress on the ion content,ratio,and transport in different parts of C.indicum strains with different salt resistance abilities were analyzed.The NHX family members and HKT genes of C.indicum were identified by bioinformatics method.The expression levels of NHX and HKT genes at different time points in the roots,stems,and leaves of C.indicum strains with different salt resistance abilities under salt stress were determined by qRT-PCR.[Result]Compared with the control group,the Na+ content in the roots,stems,and leaves of various strains varied significantly increased,and the K+ content and K+/Na+ ratio were significantly reduced.In most cases,SK+,Na+ in various parts of high and medium resistant strains were higher than that in the control group.With the decrease of salt resistance,the Na+ content in roots,stems and leaves of various strains was increasing,while the K+ content and K+/Na+ ratio were decreasing.SK+,Na+ in each part were increasing first and then decreasing.A total of 6 members of the C.indicum NHX family(CiNHX1-6)and 1 C.indicum HKT gene(CiHKT1)were identified.After salt stress,the expression of the CiNHX2 gene in the roots of high-resistant strains is significantly higher than in low-resistant strains,while the expression pattern of this gene is the same in the roots and stems of H1 and H2 strains.Similarly,the expression of the CiNHX4 gene in the roots and leaves of high-resistant strains is significantly upregulated,while the expression pattern of this gene is the same in the roots and leaves of H1 and H2 strains.The expression levels of CiNHX1,CiNHX3,CiNHX5,and CiNHX6 in the roots,stems,and leaves of each strain did not show significant changes,and the overall expression level was low.The expression level of CiNHX3 in the roots was slightly higher,and the expression levels of CiNHX1 and CiNHX6 in the leaves were slightly higher.The expression of the CiHKT1 gene in the roots and leaves of wild C.indicum was significantly affected by salt stress,and the relative expression level in high-resistant strains was significantly upregulated.[Conclusion]The stronger the salt resistance of C.indicum is,the less its ion absorption,transport and distribution are affected by salt stress.Under salt stress,the high resistant strains can effectively excrete Na+ and selectively absorb K+ thereby stabilizing the ion content and distribution in body.The medium resistant strains are relatively affected by stress,but excessive Na+ toxicity to the aboveground part can be prevented by selectively transporting K+.CiNHX2,CiNHX4,and CiHKT1 genes are closely related to the salt tolerance of wild C.indicum strains,and are the key genes for wild C.indicum to resist salt stress.