| Cotton,with salt-alkaline tolerance,is an important economic crop in China.Tocopherols are significant lipid-soluble antioxidants and can be synthesized only in phtotatuotrophy organisms.As a member of cellular antioxidant system,tocopherols play paramount roles in plant resistance to adversity stress.In this study,three upland cotton cultivars including,salt-tolerant cv.Zaoshuchangrong7,salt-sensitive cv.Nandanbadidahua,and standard cv.TM-1 were used as experimental materials.And solution culture with different concentrations of NaCl were conducted to study the effect of salt stress on characteristics of seedling growth,antioxidant enzyme activity,inorganic ions and tocopherols concentration.Candidate tocopherol biosynthetic genes in G.hirsutum acc.TM-1 were survevyed by bioinformatic analysis,and and their phylogenetic relationships,gene structures and expression patterns were analyzed too.Furthermore,to elucidate the relationships between salt tolerance and tocopherol biosynthesis on molecular mechanisms,a dedicated qPCR array for a global analysis of the expression patterns of tocopherol biosynthetic genes in different tissues of different salt-tolerant cultivars.Finally,a comprehensive analysis was conducted on the effect of physical characteristics and molecules expression under salt stress to systematically study on salt tolerance mechanism of cotton.The main results were as follows:1.Solution culture were conducted to study the effect of salt stress on characteristics of seedling growth,antioxidant enzyme activity,photosynthetic rate,MDA content and inorganic ions concentration of two upland cotton cultivars(cv.Zaoshuchangrong7,salt-tolerant and cv.Nandanbadidahua,salt-sensitive).The results indicated that salt-tolerant cotton had a larger growth quantity of root under moderate salt stress.For instance,under 150 mM NaCl treatment,the salt-tolerant cv.Zaoshuchangrong7 had 14.3%,10.9%and 21.7%more in lateral root number,root length,and root weight than the control,respectively.Also,the higher net photosynthetic rate and antioxidant enzyme activity could be maintained in the leaf of salt-tolerant cotton under salt stress.Furthermore,in the same NaCl treatment,the salt-tolerant cv.Zaoshuchangrong7 showed a regular distribution of inorganic ions concentrations:greatly higher concentration of Na+ in root than in stem and leaf;higher concentrations of K+,Ca2+,and Mg2+,but lower the ratio of Na+/K+ in shoot.It was indicated that the root of salt-tolerant cv.Zaoshuchangrong7 could store up part of Na+ in root thereby to relieve Na+toxicity to shoot.2.Three upland cotton cultivars such as salt-tolerant cv.Zaoshuchangrong7,salt-sensitive cv.Nandanbadidahua,and standard cv.TM-1 were used as materials to study the effect of salt stress on concentration and component of tocopherols in the leaves of cotton seedlings by HPLC method.The results showed,in 150 and 300 mM NaCl treatments,the concentration of total tocopherols in salt-tolerant cv.Zaoshuchangrong7 raised 2.5 and 3.4 fold than the control,respectively.Among this,the ratio of a-tocopherol increased from the control of 53.25%to 87.85%and 85.47%,respectively.It indicated that the concentration of total tocopherols was increased and a-tocopherol play a major role to alleviate oxidative damage by salt stress.3.The candidate tocopherol biosynthetic genes in G.hirsutum were identified by bioinformatic analysis.Phylogenetic relationships,gene structures and expression patterns were also conducted.Thus,a total of 23 non-redundant genes were identified.There 4,6,7,4,2 genes were in TC,HPT,MPBQ MT,y-TMT and HPPD,respectively,and unevenly distributed among 16 chromosomes of G.Hirsutum.Under salt stress,most of y-TMT genes showed high abundance expression and Ghy-TMT3 had an order of magnitude increases in the leaves of salt-tolerant cv.Zaoshuchangrong7.It suggested that salt-tolerant cotton can improve the expression level of y-TMT genes and increase the content of a-tocopherol for enhancing stress tolerance. |
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