Selective degradation processes in plants are not limited to autophagy

KEY MESSAGE: This review explores the various pathways of organelle degradation in plant cells. Besides autophagy, there are numerous other mechanisms for the selective removal of cellular components. Many of these mechanisms remain poorly understood, opening up new research avenues. Diverse degradation mechanisms of cellular components play a pivotal role in programmed cell death (PCD) during development and in response to stress. Notably, these degradation pathways can be genetically embedded in the differentiation of cells that, while remaining viable, adapt to specialized functions. Consequently, the heterogeneity of tissues and organs is shaped by intracellular destructions that lead to the autolysis of entire cells or merely a reduction of their cytoplasmic content. These degradation processes are integral to cell homeostasis, governing the requisite number of organelles and molecules through the removal of superfluous components. Autophagy is a critical process responsible for initiating and advancing this degradation. Selective autophagy meticulously identifies individual cell components destined for elimination. Despite the abundance of data regarding the functions and dynamics of this process at ultrastructural and molecular levels, the pathways involving varied degradation mechanisms in plant cells, which share common objectives, are exceedingly complex. These processes may interact with each other, be linked to autophagy, or operate independently. Furthermore, certain organelles may degenerate autonomously. Unlike selective autophagy, other degradation pathways in plant cells lack detailed descriptions. Specifically, the molecular regulation of various elimination pathways requires thorough documentation. Despite numerous discoveries through ultrastructural observations, significant gaps and uncertainties remain, necessitating further investigation. For plant cells, the descriptive collection and comparison of degradation processes have historically presented challenges, now addressed in this review.