长波紫外线对萝卜芽苗菜抗坏血酸合成的影响

EFFECTS OF ULTRAVIOLET A ON SYNTHESIS OF ASCORBIC ACID IN RADISH SPROUTS

目的研究UV-A照射对萝卜芽苗菜中抗坏血酸含量的影响。方法以黑暗为对照,将暗培养3 d后的萝卜芽苗菜连续白光和UV-A照射48 h,光照强度为(30±3)μmol·m-2·s-1,取样进行生长指标、抗坏血酸含量、酶活及合成基因表达量的测定。结果与黑暗相比,白光及UV-A处理下萝卜芽苗菜下胚轴长度显著低于对照。UV-A照射显著提高抗坏血酸含量和抗氧化酶活性。对抗坏血酸合成相关基因的定量PCR分析表明,UV-A照射下,磷酸甘露糖变位酶(PMM)、GDP-甘露糖-3’,5’-差向异构酶(GME)、磷酸二酯酶(GGP)、L-半乳糖-1-磷酸酶(GPP)、L-半乳糖酸-1,4-内酷脱氢酶(GLDH)基因表达量变化显著,且各时间段GLDH酶活性均显著高于对照和白光处理。结论 UV-A照射通过提高L-半乳糖途径相关基因表达量及GLDH酶活性提高萝卜芽苗菜中抗坏血酸含量。

ObjectiveTo understand the effects of UV-A on ascorbic acid content in radish sprouts. MethodAfter growingin darkness for three days, radish sprouts were cultured under white light and UV-A for 48 h. The photon flux density was （30 ± 3）μmol·m^-2·s^-1. The dark treatment was used as the control. Samples were collected to assessthe growth index, ascorbic acid content, enzyme activity and the expression of related synthetic genes.ResultsCompared with the control, white and UV-A radiations significantly decreased hypocotyl length of radish sprouts. UV-A radiation significantly increased ascorbic acid content as well as the activity of antioxidant enzymes. From the quantitative PCR analysis of the synthetic genes of ascorbic acid,we found that UV-A radiation significantly increased the expression of related synthetic genes, such asphosphomannose mutase （PMM）, GDP-D-mannose-3,,5,-epimerase （GME）, GDP-L-galactose phosphorylase （GGP）, L-galactose-1-phosphate phosphatase （GPP）,L-galactono-1,4-lactone dehydrogenase （GLDH）. Furthermore, GLDH activity was significantly higher under UV-A radiation than that of white radiation during each experiment time frame. ConclusionUV-A radiation increases the content of ascorbic acid by up-regulating the expression of related genes in L-galactose pathway and the activity of GLDH in radish sprouts.