Galactolipids Are Essential for Internal Membrane Transformation during Etioplast-to-Chloroplast Differentiation
Galactolipids Are Essential for Internal Membrane Transformation during Etioplast-to-Chloroplast Differentiation
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DOI：
10.1093/pcp/pcz041
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发表时间：
2019-06-01
影响因子：
4.9
通讯作者：
Kobayashi, Koichi
中科院分区：
文献类型：
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作者：
Fujii, Sho;Nagata, Noriko;Kobayashi, Koichi
被子植物子叶细胞在黑暗中发育的真质体在光照下迅速分化为叶绿体。这一过程涉及到内部膜结构的动态转换，从原片层体（PLBs）和类囊体（PT）在叶绿体类囊体膜。虽然两个半乳糖脂，monogalactosyldiacylglycerol（MGDG）和digalactosyldiacylglycerol（DGDG），是主要的脂质成分的膜在两个叶绿体和叶绿体，它们的作用在结构和功能的转化过程中的内膜的叶绿体分化是未知的。我们先前报道了通过靶向主要MGDG合酶（amiR-MGD 1）的人工microRNA导致的36%的MGDG损失仅轻微影响PLB结构，但强烈损害PT形成和原叶绿酸生物合成。与此同时，DGDG合成酶突变体（dgd 1）中的DGDG缺陷除了损害PT发育和原叶绿素合成外，还扰乱了PLB晶格结构。在这项研究中，类囊体生物合成后PLB拆卸照明强烈扰动amiR-MGD 1。amiR-MGD 1的表达损害了Chl和主要捕光复合物II蛋白（LHCB 1）的积累，这可能会抑制从拆解的PLBs到类囊体膜的快速转化。正如amiR-MGD 1表达一样，dgd 1突变损害了叶绿体向叶绿体分化过程中Chl和LHCB 1的积累。此外，与amiR-MGD 1幼苗不同，在dgd 1幼苗中，光照后PLBs的分解被延迟。由于DGDG而不是MGDG更倾向于在膜中形成双层脂相，因此MGDG与DGDG的比例可能强烈地影响在叶绿体向叶绿体分化过程中PLBs向类囊体膜的转化。
Etioplasts developed in angiosperm cotyledon cells in darkness rapidly differentiate into chloroplasts with illumination. This process involves dynamic transformation of internal membrane structures from the prolamellar bodies ( PLBs) and prothylakoids ( PTs) in etioplasts to thylakoid membranes in chloroplasts. Although two galactolipids, monogalactosyldiacylglycerol ( MGDG) and digalactosyldiacylglycerol ( DGDG), are predominant lipid constituents of membranes in both etioplasts and chloroplasts, their roles in the structural and functional transformation of internal membranes during etioplast-to-chloroplast differentiation are unknown. We previously reported that a 36% loss of MGDG by an artificial microRNA targeting major MGDG synthase ( amiR-MGD1) only slightly affected PLB structures but strongly impaired PT formation and protochlorophyllide biosynthesis. Meanwhile, strong DGDG deficiency in a DGDG synthase mutant ( dgd1) disordered the PLB lattice structure in addition to impaired PT development and protochlorophyllide biosynthesis. In this study, thylakoid biogenesis after PLB disassembly with illumination was strongly perturbed by amiR-MGD1. The amiR-MGD1 expression impaired the accumulation of Chl and the major light-harvesting complex II protein ( LHCB1), which may inhibit rapid transformation from disassembled PLBs to the thylakoid membrane. As did amiR-MGD1 expression, dgd1 mutation impaired the accumulation of Chl and LHCB1 during etioplast-to-chloroplast differentiation. Furthermore, unlike in amiR-MGD1 seedlings, in dgd1 seedlings, disassembly of PLBs after illumination was retarded. Because DGDG but not MGDG prefers to form the bilayer lipid phase in membranes, the MGDG-to-DGDG ratio may strongly affect the transformation of PLBs to the thylakoid membrane during etioplast-to-chloroplast differentiation.