Lopez-Juez Enrique, Pyke Kevin A
School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK.
Int J Dev Biol. 2005;49(5-6):557-77. doi: 10.1387/ijdb.051997el.
Derived by endosymbiosis from ancestral cyanobacteria, chloroplasts integrated seamlessly into the biology of their host cell. That integration involved a massive transfer of genes to the cell's nucleus, with the modification of pre-existing processes, like plastid division and the operation of the plastid genetic machinery and the emergence of new ones, like the import of proteins translated in the cytoplasm. The uncovering in molecular detail of several of these processes reveals a merger of mechanisms of symbiont and host origin. Chloroplasts acquired roles as part of the biology of land plants by differentiating into a variety of interconvertible plastid forms according to the cell type. How these conversions take place, or how new problems, like the regulation of the plastid population size in cells, have been solved, is barely starting to be understood. Like the whole plant and as a result of the requirements and dangers associated with photosynthetic activity, chloroplasts in particular are under the control of environmental cues. Far from being passive targets of cellular processes, plastids are sources of signals of plastid-nuclear communication, which regulate activities for their own biogenesis. Plastids are also sources of developmental signals, in whose absence tissue architecture or cell differentiation are aberrant, in a cell-autonomous fashion. Over evolutionary time, plastids also contributed many genes for activities that are no longer directly associated with them (like light perception or hormone function). The overall picture is one in which plastids are at both the receiving and the acting ends in plant development, in both ontogenic and evolutionary terms.
叶绿体由祖先蓝细菌通过内共生衍生而来，无缝融入宿主细胞的生物学过程。这种整合涉及大量基因向细胞核的转移，同时对诸如质体分裂、质体遗传机制的运作等先前存在的过程进行了修饰，并出现了新的过程，如细胞质中翻译的蛋白质的导入。对其中几个过程的分子细节的揭示，展现了共生体和宿主起源机制的融合。叶绿体通过根据细胞类型分化为多种可相互转化的质体形式，成为陆地植物生物学的一部分。这些转化如何发生，或者像细胞中质体群体大小的调控等新问题是如何解决的，才刚刚开始被理解。与整个植物一样，由于与光合作用活动相关的需求和危险，叶绿体尤其受到环境信号的控制。质体远非细胞过程的被动靶点，而是质体 - 核通信信号的来源，这些信号调节着它们自身生物发生的活动。质体也是发育信号的来源，在缺乏这些信号时，组织结构或细胞分化会以细胞自主的方式出现异常。在进化过程中，质体还为许多不再与它们直接相关的活动（如光感知或激素功能）贡献了许多基因。总体情况是，从个体发育和进化的角度来看，质体在植物发育中既处于接收端又处于作用端。
