低温胁迫对木薯叶片叶绿素荧光参数及PSⅡ相关蛋白表达水平的影响

Influence of low temperature stress on chlorophyll fluorescence parameters and expression levels of proteins in PSⅡof cassava

以木薯栽培种华南8号(cv.SC8)盆栽苗为材料,研究5℃低温胁迫7 d期间叶片叶绿素含量及荧光参数、光系统Ⅱ(PSⅡ)相关蛋白表达水平的动态变化。结果表明:随着胁迫时间的延长,叶绿素a和叶绿素b含量均先下降后缓慢升高,且均在处理2 d后达到最低;低温胁迫期间,最大光合效率(Fv/Fm)、光化学量子效率(ΦPSⅡ)、光化学淬灭系数(qP)、非光化学淬灭系数(NPQ)及光合电子传递速率(ETR)均显著下降,其中Fv/Fm持续下降,ΦPSⅡ、qP和ETR在胁迫2 d后达到最低后缓慢上升,NPQ在胁迫5 d后达到最低;叶绿素含量、叶绿素荧光参数显著下降表明,胁迫后PSⅡ反应中心捕光能力、开放程度及光化学转化效率显著下降,从而抑制了叶片的光合速率;PSⅡ中D1、D2、放氧复合体(OEC)及核酮糖–1,5–二磷酸羧化酶/加氧酶(Rubisco)的表达水平均在低温胁迫2 d后达到最低水平,且D1蛋白下调显著;PSⅡ中相关蛋白表达水平下调,也在蛋白质水平上验证了低温胁迫抑制叶片的光合速率。

Potting seedling of cassava cultivar SC8 was used as materials to investigate the changes of leave chlorophyll content, chlorophyll fluorescence parameters and the expressions of proteins in PSⅡ of cassava seedlings exposed to low temperature （5 ℃） for 7 days. The results show that during the stress, chlorophyll a and chlorophyll b contents were both decreased first and then slowly increased, reaching the minimum 2 days after stress; maximum photochemical efficiency （Fv/Fm）, photochemical quantum efficiency of photosystem Ⅱ （ФPSⅡ）, photochemical quenching （qp）, non-photochemical quenching （NPQ） and electron transport rate （ETR） were significantly decreased with Fv/Fm continuously declined, while ФPSⅡ, qP and ETR first decreased to minimum level 2 days after stress, and then slowly rose, and NPQ decreased to minimum level 5 days after stress. The significant decrease of chlorophyll content and chlorophyll fluorescence parameters indicate that the light-harvesting ability, openness and photochemical conversion rate in PSⅡ reaction center were decreased significantly, which inhibiting the photosynthetic efficiency of cassava leaves. The expression level of D 1 D2, OEC and Rubisco reached the lowest 2 days after stress with D 1 decreased significantly. The down-regulation of the expression of proteins in PS II verifies at protein level that low temperature inhibits photosynthesis of leaves.