Aranda-Sicilia María Nieves, Aboukila Ali, Armbruster Ute, Cagnac Olivier, Schumann Tobias, Kunz Hans-Henning, Jahns Peter, Rodríguez-Rosales María Pilar, Sze Heven, Venema Kees
Departimento de Bioquímica, Biología Celular, y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain (M.N.A.-S., A.A., O.C., M.P.R.-R., K.V.);Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (U.A.);Institute of Plant Biochemistry, Heinrich-Heine-University Düsseldorf, D-40225 Duesseldorf, Germany (T.S., P.J.);School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236 (H.-H.K.); andDepartment of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (H.S.).
Departimento de Bioquímica, Biología Celular, y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, 18008 Granada, Spain (M.N.A.-S., A.A., O.C., M.P.R.-R., K.V.);Howard Hughes Medical Institute, Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (U.A.);Institute of Plant Biochemistry, Heinrich-Heine-University Düsseldorf, D-40225 Duesseldorf, Germany (T.S., P.J.);School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236 (H.-H.K.); andDepartment of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742 (H.S.)
Plant Physiol. 2016 Sep;172(1):441-9. doi: 10.1104/pp.16.00995. Epub 2016 Jul 21.
It is well established that thylakoid membranes of chloroplasts convert light energy into chemical energy, yet the development of chloroplast and thylakoid membranes is poorly understood. Loss of function of the two envelope K(+)/H(+) antiporters AtKEA1 and AtKEA2 was shown previously to have negative effects on the efficiency of photosynthesis and plant growth; however, the molecular basis remained unclear. Here, we tested whether the previously described phenotypes of double mutant kea1kea2 plants are due in part to defects during early chloroplast development in Arabidopsis (Arabidopsis thaliana). We show that impaired growth and pigmentation is particularly evident in young expanding leaves of kea1kea2 mutants. In proliferating leaf zones, chloroplasts contain much lower amounts of photosynthetic complexes and chlorophyll. Strikingly, AtKEA1 and AtKEA2 proteins accumulate to high amounts in small and dividing plastids, where they are specifically localized to the two caps of the organelle separated by the fission plane. The unusually long amino-terminal domain of 550 residues that precedes the antiport domain appears to tether the full-length AtKEA2 protein to the two caps. Finally, we show that the double mutant contains 30% fewer chloroplasts per cell. Together, these results show that AtKEA1 and AtKEA2 transporters in specific microdomains of the inner envelope link local osmotic, ionic, and pH homeostasis to plastid division and thylakoid membrane formation.
叶绿体的类囊体膜可将光能转化为化学能，这一点已得到充分证实，然而，叶绿体和类囊体膜的发育却鲜为人知。此前研究表明，两个包膜K(+)/H(+)反向转运蛋白AtKEA1和AtKEA2的功能丧失对光合作用效率和植物生长有负面影响；然而，其分子基础仍不清楚。在这里，我们测试了先前描述的kea1kea2双突变体植物的表型是否部分归因于拟南芥早期叶绿体发育过程中的缺陷。我们发现，kea1kea2突变体幼嫩的展开叶片中生长和色素沉着受损尤为明显。在增殖的叶区，叶绿体中光合复合体和叶绿素的含量要低得多。令人惊讶的是，AtKEA1和AtKEA2蛋白在小的、正在分裂的质体中大量积累，它们特异性地定位于由分裂平面分隔的细胞器的两个帽状结构处。反向转运结构域之前异常长的550个残基的氨基末端结构域似乎将全长AtKEA2蛋白系于这两个帽状结构上。最后，我们发现双突变体细胞中的叶绿体数量少30%。总之，这些结果表明，内膜特定微区中的AtKEA1和AtKEA2转运蛋白将局部渗透、离子和pH稳态与质体分裂和类囊体膜形成联系起来。
