Department of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06511, USA.
Department of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06511, USA.
J Plant Physiol. 2014 Feb 15;171(3-4):311-8. doi: 10.1016/j.jplph.2013.09.007. Epub 2013 Oct 10.
The nuclear LHCB7 gene is common in higher plants, encodes a transcript that is well expressed in a subset of leaf mesophyll cells, and is associated with a protein product that is homologous to pigment-binding components of the photosystem (PS) II peripheral antenna complex. We compared the physiological properties of wild type and LHCB7-deficient leaves [DNA insertion, Arabidopsis thaliana (At) ecotype Columbia] in terms of pigment content, CO2 exchange, in vivo transmittance at 810 nm, and chlorophyll fluorescence. The latter two techniques are functional indicators for PSI and PSII, respectively. Key features of the mutant phenotype were confirmed using antisense technology and a hemizygote of two independent AtLHCB7 DNA insertion lines. Growth, leaf pigment composition, white light absorptance, and levels of AtLHCB1-6 were not significantly different in the mutant compared to wild type. Likewise, neither intrinsic PSII light capture efficiency nor partitioning of absorbed radiation to PSII was affected by the mutation. The absence of AtLHCB7 is associated with lower rates of light-saturated photosynthesis and a diminished irradiance threshold for induction of photoprotective non-photochemical quenching. Overall, the pattern of change in light utilization parameters and plastoquinol level indicated that loss of AtLHCB7 expression led to slower Rubisco turnover characterized by pH-dependent balancing of electron transport to reduced carbon assimilation capacity (photosynthetic control). No effect of AtLHCB7 genotype on xanthophyll de-epoxidation state was detected suggesting that factors in addition to lumenal pH influence zeaxanthin accumulation.
核 LHCB7 基因在高等植物中很常见，编码一种在部分叶肉细胞中表达良好的转录本，与一种与光合系统 (PS) II 外周天线复合物的色素结合成分同源的蛋白质产物相关。我们比较了野生型和 LHCB7 缺陷型叶片（DNA 插入，拟南芥哥伦比亚生态型）在色素含量、CO2 交换、810nm 下的体内透过率和叶绿素荧光方面的生理特性。后两种技术分别是 PSI 和 PSII 的功能指标。使用反义技术和两个独立的 AtLHCB7 DNA 插入系的半合子，证实了突变体表型的关键特征。与野生型相比，突变体的生长、叶片色素组成、白光吸收率和 AtLHCB1-6 水平没有显著差异。同样，内在 PSII 光捕获效率或吸收辐射到 PSII 的分配也不受突变的影响。AtLHCB7 的缺失与光饱和光合作用的较低速率以及光保护非光化学猝灭的诱导辐照度阈值降低有关。总的来说，光利用参数和质体醌水平的变化模式表明，AtLHCB7 表达的丧失导致 Rubisco 周转率减慢，其特征是电子传递对还原碳同化能力（光合作用控制）的 pH 依赖性平衡。未检测到 AtLHCB7 基因型对叶黄素去环氧化态的影响，这表明除了腔室 pH 之外，还有其他因素影响玉米黄质的积累。
