过量锰处理对柱花草次级代谢物、酶活性和SgPALs基因表达的影响

Effects of Excess Manganese on Secondary Metabolites, Enzyme Activity and Sg PALs Gene Expression in Stylosanthes

以热研二号(RY2)柱花草为材料,分析过量锰处理(100~600μmol/L)对柱花草生长、次级代谢物、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)及SgPALs基因表达的影响,探讨金属锰毒害对柱花草次级代谢途径的影响。结果表明:相对对照锰(5μmol/L)处理,400、600μmol/L锰处理显著抑制柱花草叶片叶绿素浓度、最大光化合速率(F_v/F_m)、地上部和根部生物量。随着外源锰处理浓度(100~600μmol/L)的增加,叶片原花青素、总酚和单宁含量呈现出逐渐增加的趋势,而叶片类黄酮含量逐渐降低。此外,400、600μmol/L锰处理显著增加叶片PAL酶活性,但对PPO活性影响不明显。定量PCR结果表明,过量锰处理对SgPAL1和SgPAL2基因表达影响不明显,但过量锰处理增强了SgPAL3和SgPAL4基因在柱花草叶片中的表达。以上结果说明,柱花草可能通过苯丙氨酸途径调控次级代谢响应金属锰毒胁迫,且SgPAL3和SgPAL4基因可能参与该响应过程。研究结果为探索柱花草响应金属锰毒胁迫机理提供重要依据。

In this study, the effects of different manganese(Mn) levels on the growth, chlorophyll content, secondary metabolites and activities of polyphenol oxidase(PPO) and phenylalnine ammonialyase(PAL) as well as SgPALs expressions were investigated using Stylosanthes(stylo) genotype RY2. Results showed that the chlorophyll concentration, maximum photochemical rate(F_v/F_m), shoot and root dry weight of stylo significantly decreased by 400 μmol/L and 600 μmol/L Mn treatments. The contents of proanthocyanidin, total phenol and tannin increased but the flavonoid content decreased in the leaves ranged from 100 μmol/L to 600 μmol/L. Furthermore, the activities of PAL, except PPO, increased under 400 μmol/L and 600 μmol/L Mn treatments compared to that in the 5 μmol/L Mn treatment. qRT-PCR analysis showed that the expressions of SgPAL3 and SgPAL4 in the leaves were significantly enhanced by excess Mn treatments, in despite of the expressions of SgPAL1 and SgPAL2 were not regulated by Mn. The results suggested that the regulation of the secondary metabolites through SgPALs mediated phenylalanine pathway might be involved in the response to Mn toxicity in stylo. The study would provide an important basis for exploring the mechanisms of stylo in response to Mn toxicity.