低温胁迫对乐都紫皮大蒜生长及果聚糖代谢关键酶基因的影响

Effects of low temperature stress on the growth and key enzyme genes of garlic metabolism in garlic

果聚糖的代谢过程不仅影响大蒜的产量和品质,也能有效地提高大蒜植株的抗逆性。为探讨低温胁迫对大蒜生长和果聚糖代谢酶基因表达的影响,本试验以乐都紫皮大蒜为试验材料,在正常培养(25℃)和低温胁迫(4℃)下探究大蒜幼苗处理0、3、6、9和12 d时的生长指标变化特征及蔗糖∶蔗糖1-果糖基转移酶基因(1-SST)与果聚糖外切水解酶基因(1-FEH)的表达特性。结果表明:(1)低温胁迫对乐都紫皮大蒜幼苗生长产生了抑制作用,胁迫3 d时,乐都紫皮大蒜幼苗的株高、最大叶长、最大叶宽和茎高分别比对照降低了43. 45%、42. 22%、17. 63%和58. 10%,随后降低幅度变缓。(2)随着胁迫时间的延长,低温处理使1-SST基因和1-FEH基因表达量显著升高,且在胁迫第6天时达到最高值。1-SST基因和1-FEH基因的表达量分别是对照的45倍和7. 56倍;1-FEH基因表达量显著低于1-SST基因的表达量,故低温胁迫下果聚糖代谢酶关键基因的表达过程是一个"以合成为主,以水解为辐"的过程。低温胁迫抑制了乐都紫皮大蒜幼苗的生长,胁迫第6天是幼苗响应低温的关键时期,并推测乐都紫皮大蒜主要通过增强果聚糖的合成来响应低温胁迫。

The metabolic process of fructan not only affects the yield and quality of garlic,but also effectively improves the resistance of the plants.In order to investigate the effects of low temperature stress on the growth of garlic and the expression of fructan metabolizing enzymes,Ledu purple skin garlic was used as a test material to explore garlic seedlings under normal culture(25℃)and low temperature stress(4℃).The characteristics of garlic seedlings growth and sucrose:sucrose 1-fructosyltransferase gene(1-SST)and fructan exohydrolase gene(1-FEH)expressions on stress treatment of 0,3,6,9,12 d were studied.The results showed that:(1)Low temperature stress played the inhibition role on the growth of garlic seedlings.Stress treatment for 3 days decreased the plant height,maximum leaf length,maximum leaf width and stem height by 43.45%,42.22%,17.63%and 58.10%compared with that of control,respectively.Thereafter,the decrease extent of growth indexes reduced gradually.(2)With the stress time extending,the expression of 1-SST and 1-FEH was significantly increased by low temperature stress,and reached the highest value at 6d.The expression levels of 1-SST and 1-FEH under treating 6 days were 45 times and 7.56 times of the control,respectively.During the whole treatment,the expression level of 1-FEH gene was significantly lower than that of 1-SST gene.So the period of key gene of fructan metabolizing enzyme expression under low temperature stress was a process of“synthesis-main,hydrolysis-secondary”.low temperature stress inhibited the growth of garlic seedlings.Therefore,6 d treatment was a critical period for seedlings responsing to low temperature.It is speculated that garlic seedlings respond to low temperature stress by enhancing the synthesis of fructan.