Department of Horticulture, Washington State University, Pullman, WA, USA.
Molecular Plant Science Graduate Program, Washington State University, Pullman, WA, USA.
Plant Cell Rep. 2017 Oct;36(10):1627-1640. doi: 10.1007/s00299-017-2179-z. Epub 2017 Jul 11.
Comparative ultrastructural developmental time-course analysis has identified discrete stages at which the fruit plastids undergo structural and consequently functional transitions to facilitate subsequent development-guided understanding of the complex plastid biology. Plastids are the defining organelle for a plant cell and are critical for myriad metabolic functions. The role of leaf plastid, chloroplast, is extensively documented; however, fruit plastids-chromoplasts-are poorly understood, especially in the context of the diverse metabolic processes operating in these diverse plant organs. Recently, in a comparative study of the predicted plastid-targeted proteomes across seven plant species, we reported that each plant species is predicted to harbor a unique set of plastid-targeted proteins. However, the temporal and developmental context of these processes remains unknown. In this study, an ultrastructural analysis approach was used to characterize fruit plastids in the epidermal and collenchymal cell layers at 11 developmental timepoints in three genotypes of apple (Malus × domestica Borkh.): chlorophyll-predominant 'Granny Smith', carotenoid-predominant 'Golden Delicious', and anthocyanin-predominant 'Top Red Delicious'. Plastids transitioned from a proplastid-like plastid to a chromoplast-like plastid in epidermis cells, while in the collenchyma cells, they transitioned from a chloroplast-like plastid to a chloro-chromo-amyloplast plastid. Plastids in the collenchyma cells of the three genotypes demonstrated a diverse array of structures and features. This study enabled the identification of discrete developmental stages during which specific functions are most likely being performed by the plastids as indicated by accumulation of plastoglobuli, starch granules, and other sub-organeller structures. Information regarding the metabolically active developmental stages is expected to facilitate biologically relevant omics studies to unravel the complex biochemistry of plastids in perennial non-model systems.
比较超微结构发育时间进程分析已经确定了果实质体在结构上发生的离散阶段转变，这些转变有助于随后对质体生物学的复杂发展进行指导理解。质体是植物细胞的定义性细胞器，对无数代谢功能至关重要。叶质体（叶绿体）的作用得到了广泛的证明；然而，果实质体（有色体）的了解甚少，尤其是在这些不同植物器官中进行的多种代谢过程的背景下。最近，在对七个植物物种的预测质体靶向蛋白质组进行的比较研究中，我们报告说，每种植物物种都被预测具有独特的一套质体靶向蛋白质。然而，这些过程的时间和发育背景仍然未知。在这项研究中，使用超微结构分析方法来描述在三个苹果（Malus × domestica Borkh.）基因型的 11 个发育时间点中表皮和韧皮细胞层中的果实质体：叶绿素占优势的“青苹果”，类胡萝卜素占优势的“金元帅”和花青素占优势的“元帅红”。在表皮细胞中，质体从原质体样质体向有色体样质体转变，而在韧皮细胞中，它们从叶绿体样质体向氯-类淀粉质体转变。三个基因型的韧皮细胞中的质体表现出多种多样的结构和特征。这项研究使我们能够确定在特定功能最有可能由质体执行的离散发育阶段，这是通过质体小球体、淀粉粒和其他亚细胞器结构的积累来指示的。有关代谢活跃发育阶段的信息预计将有助于进行生物学上相关的组学研究，以揭示多年生非模式系统中质体的复杂生物化学。
