逆境胁迫对樟叶越桔CA的影响及调控机制

Vaccinium dunalianum (Ericaceae) with various physiological activities is one of the main plant sources of arbutin which widely used in cosmetic formulations as natural active agents to whiten the skin because of control of the formation of melanin. The previous studies found 6'-O-caffeoylarbutin(CA) with rare high content of 23% (dry weight) appeared in the buds of V.dunalianum from Wuding, Yunnan, China and had higher physiological activities than arbutin. It would be possible that mass production of natural arbutin would be achieved. However, CA content decreased significantly in V. dunalianum from Wuding County after introduction and cultivation and the reasons for this phenomenon remain unclear. It is speculated that abiotic stress would influence the content of CA,but with no experimental evidence. Based on previous studies, the project will compare the differences in CA content, physiological property and gene expression in V. dunalianum under different environmental conditions in controlled greenhouse thorough chemical biology, physiological ecology and molecular biology approaches. The main aims are to understand the primary environmental factor and physiological and metabolic processes affecting the content of CA of V. dunalianum. These results will be beneficial for illuminating the correlation of the environments with the accumulation of CA, and developing effective strategy for commercial cultivation and variety breeding of CA high-yield plant V. dunalianum.

具有多方面生理活性的樟叶越桔是广泛应用于化妆品行业的皮肤美白天然活性剂原料熊果苷的主要植物来源之一。前期研究发现，优于熊果苷生理活性的6'-O-咖啡酰熊果苷（CA）以干重23%的罕见高含量存在于云南省武定县野生樟叶越桔叶芽中，这为大量生产天然的熊果苷类衍生物提供了可能。将武定县野生樟叶越桔引种栽培后发现叶芽中CA含量显著下降，推测环境胁迫是导致其引种栽培前后CA含量差异显著的主要因素，但仍缺乏实验证据。本项目拟在前期工作基础上，采用化学生物学、生理生态和分子生物学等方法，研究樟叶越桔在不同逆境胁迫下CA含量变化、生理特性和基因表达差异，阐明影响樟叶越桔CA含量变化的关键限制因素及调控机制，为樟叶越桔的引种驯化和品种选育提供科学依据。

樟叶越桔是一种富含CA、熊果苷和绿原酸的特殊资源植物。熊果苷已作为美白活性添加剂广泛运用于祛斑化妆品中。CA作为熊果苷的衍生物，抑制黑色素合成活性优于熊果苷，且毒性仅为熊果苷的1/2，因此CA有望成为更加理想的皮肤美白类化妆品添加剂。将野生樟叶越桔引种栽培后发现CA含量显著下降，推测环境胁迫是导致其CA含量差异显著的主要因素。本项目揭示了光照、温度、土壤水分和钙、钾、镁、铜、锰营养元素等8种环境因子对樟叶越桔CA含量的影响。强度光照对熊果苷和绿原酸含量没有显著影响，对CA含量影响不规律。零上低温胁迫能促进CA、熊果苷和绿原酸含量增加。高温胁迫显著促进熊果苷含量积累，但显著抑制CA和绿原酸的积累。轻度干旱（一周左右）下CA含量增加，深度干旱（一月左右）胁迫下熊果苷和绿原酸含量增加。不同营养元素单因素实验不同浓度处理下，71.250μg/L KNO3和38.096μg/L MgSO4分别处理时CA、熊果苷和绿原酸三种化合物含量最高，CA含量分别高达干重的5%和4.58%；7.550μg/L MnSO4和0.032μg/L CuSO4分别处理时CA和熊果苷含量最高，CA含量分别达干重的3.27%和3.02%；131.327 μg/L CaCl2处理时CA、熊果苷和绿原酸三种化合物含量最高，但CA含量只有干重的0.84%。分子生物学实验结果表明酰基CoA、绿原酸、及HCA-Glc可能作为酰基供体，熊果苷作为受体，在VdAT基因家族表达产物催化下合成了樟叶越桔CA，而VdAT2基因表达产物可能主要参与了CA合成，VdAS1基因表达产物可能主要参与了樟叶越桔熊果苷的合成。综上所述，樟叶越桔CA含量积累受多因素影响，而温度和钾、镁等土壤营养元素可能是主要的影响因子。研究结果为高产CA樟叶越桔的引种驯化和品种选育提供了实验基础。