Ruban A V, Phillip D, Young A J, Horton P
Robert Hill Institute for Photosynthetic Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, U.K.
Biochemistry. 1997 Jun 24;36(25):7855-9. doi: 10.1021/bi9630725.
Under many environmental conditions, plants are exposed to levels of sunlight in excess of those required for photosynthesis. Then, a regulated increase in the rate of nonradiative dissipation of excess excitation energy in the thylakoid membrane correlates with the conversion of the carotenoid violaxanthin into zeaxanthin and provides protection from the damaging effects of excessive irradiation. The hypothesis that these carotenoids specifically control the oligomerization of the light harvesting complexes of photosystem II was tested by investigating the effects of violaxanthin and zeaxanthin on the behavior of the major complex, LHCIIb, on sucrose gradients; it was found that zeaxanthin stimulated the formation of LHCIIb aggregates with reduced chlorophyll fluorescence yield whereas violaxanthin caused the inhibition of such aggregation and an elevation of fluorescence. Measurements of 77 K fluorescence indicated that zeaxanthin was not exerting an additional direct quenching of chlorophyll fluorescence. These effects can explain the physiological control of the light harvesting system by the xanthophyll cycle.
在许多环境条件下，植物所接受的阳光强度超过了光合作用所需的水平。此时，类囊体膜中过量激发能的非辐射耗散速率的调节性增加与类胡萝卜素紫黄质向玉米黄质的转化相关，并能保护植物免受过度光照的损害。通过研究紫黄质和玉米黄质对主要复合物LHCIIb在蔗糖梯度上行为的影响，对这些类胡萝卜素特异性控制光系统II捕光复合物寡聚化的假说进行了验证；结果发现，玉米黄质刺激了LHCIIb聚集体的形成，同时叶绿素荧光产量降低，而紫黄质则抑制了这种聚集并导致荧光增强。77K荧光测量表明，玉米黄质并未对叶绿素荧光产生额外的直接猝灭作用。这些效应可以解释叶黄素循环对捕光系统的生理调控。
