Abdel-Ghany Salah Esmat
Biology Department, Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA.
Planta. 2009 Mar;229(4):767-79. doi: 10.1007/s00425-008-0869-z. Epub 2008 Dec 16.
In land plants plastocyanin is indispensable and therefore copper (Cu) availability is a prerequisite for growth. When Cu supply is limited, higher plants prioritize the Cu delivery to plastocyanin by down-regulation of other Cu proteins. Arabidopsis has two plastocyanin genes (PETE1 and PETE2). PETE2 is the predominant isoform in soil-grown plants and in hydroponic cultures it is accumulated in response to Cu addition. It functions as a Cu sink when more Cu is available, in addition to its role as an electron carrier. PETE1 is not affected by Cu feeding and it is the isoform that drives electron transport under Cu-deficiency. Cu feeding rescued the defect in photosystem II electron flux (Phi(PSII)) in the pete1 mutant whereas Phi(PSII) was not changed in the pete2 mutant as Cu was added. Plants with mutations in the plastocyanin genes had altered Cu homeostasis. The pete2 mutant accumulated more Cu/Zn superoxide dismutase (CSD2 and CSD1) and Cu chaperone (CCS) whereas the pete1 mutant accumulated less. On the other hand, less iron superoxide dismutase (FeSOD) and microRNA398b were observed in the pete2 mutant, whereas more were accumulated in the pete1 mutant. Our data suggest that plastocyanin isoforms are different in their response to Cu and the absence of either one changes the Cu homeostasis. Also a small amount of plastocyanin is enough to support efficient electron transport and more PETE2 is accumulated as more Cu is added, presumably, to buffer the excess Cu.
在陆生植物中，质体蓝素是不可或缺的，因此铜（Cu）的可利用性是生长的先决条件。当铜供应受到限制时，高等植物会通过下调其他铜蛋白，优先将铜输送到质体蓝素。拟南芥有两个质体蓝素基因（PETE1和PETE2）。PETE2是土壤种植植物和水培培养物中的主要异构体，在添加铜时会积累。除了作为电子载体的作用外，当有更多铜可用时，它还作为铜库发挥作用。PETE1不受铜供应的影响，它是在铜缺乏时驱动电子传递的异构体。添加铜后，铜供应挽救了pete1突变体中光系统II电子通量（Phi(PSII)）的缺陷，而在pete2突变体中添加铜时Phi(PSII)没有变化。质体蓝素基因突变的植物改变了铜稳态。pete2突变体积累了更多的铜/锌超氧化物歧化酶（CSD2和CSD1）和铜伴侣（CCS），而pete1突变体积累较少。另一方面，在pete2突变体中观察到较少的铁超氧化物歧化酶（FeSOD）和微小RNA398b，而在pete1突变体中积累较多。我们的数据表明，质体蓝素异构体对铜的反应不同，缺少任何一种都会改变铜稳态。此外，少量的质体蓝素就足以支持有效的电子传递，并且随着添加更多的铜，会积累更多的PETE2，大概是为了缓冲过量的铜。
