Transition dynamics in plastid interconversion in land plants

In land plants, plastids acquired different functions and structures in parallel with the increasing genetic, developmental, and morphological diversity attained by the plant tissues. There are transition dynamics among the morpho-functional features of the different plastid types. This review is focused on plastid structure and interconversion with a focus on recent findings and a special attention to plastid types that are less known than chloroplasts. The morpho-physiological and biochemical differences, which explain the multiple functions of each plastid type and the transcriptional and post-translational modulation of plastid capabilities are here described. The structural dynamism of plastids is also discussed through their ability to produce protrusions called stromules and the activity of lipoprotein particles known as plastoglobules. As a consequence of the proteome differences among plastid types, the conversion from one type of plastid to another requires an organellar proteome reorganization with a turnover of plastid proteins, but also a differentially regulated import of nuclear-encoded proteins. Plastid degradation by macroautophagy and microautophagy pathways is also described. Taken together, all this information allows us to interpret plastids as sensors in development and plastid interconversion as a way that the plant uses to modify its growth.