Autophagy in Development and Stress Responses of Plants

Abstract

The uptake and degradation of cytoplasmic material by vacuolar autophagy in plants has been studied extensively by electron microscopy and shown to be involved in developmental processes such as vacuole formation, deposition of seed storage proteins and senescence, and in the response of plants to nutrient starvation and to pathogens. The isolation of genes required for autophagy in yeast has allowed the identification of many of the corresponding Arabidopsis genes based on sequence similarity. Knockout mutations in some of these Arabidopsis genes have revealed physiological roles for autophagy in nutrient recycling during nitrogen deficiency and in senescence. Recently, markers for monitoring autophagy in whole plants have been developed, opening the way for future studies to decipher the mechanisms and pathways of autophagy, and the function of these pathways in plant development and stress responses.

Autophagy-Related Proteins Are Required for Degradation of Peroxisomes inArabidopsisHypocotyls during Seedling Growth

“…Alternatively, peroxisomes may be delivered to the vacuole also via unknown autophagic routes that are not associated with ATG8 but still require ATG7 (Figures 3D and 4J). One of the possible routes is protrusion microautophagy involving a direct engulfment of whole organelles by the tonoplast (Bassham et al, 2006). If protrusion microautophagy of peroxisomes is a major autophagic route for peroxisomal degradation, peroxisomes stabilized by CA should be enclosed by the tonoplast.…”

Role of plant autophagy in stress response

“…Only plant ATG4 and ATG6 complement yeast knockouts in function (Hanaoka et al, 2002;Liu et al, 2005). Two putative ATG13 genes were found in Arabidopsis, but their similarity is restricted to a relatively small region of the protein and it is currently unclear if they are true ATG13 orthologs (Bassham et al, 2006). Recently, rice and maize ATG genes have also been identified and have been characterized (Su et al, 2006;Chung et al, 2009;Xia et al, 2011).…”

“…A single homologue of VPS34 and VPS15 seems to exist in Arabidopsis, which is required for kinase activity (Bassham et al, 2006). However, ATG14, a specific autophagic constituent of the PI3K complex, has not been identified in Arabidopsis.…”

“…Previous studies have proven that sucrose starvation in suspension-cultured cells is an excellent model system for analyzing plant autophagy (Bassham et al, 2006). Autophagy is clearly upregulated during periods of starvation and darkness.…”

Autophagic Components Contribute to Hypersensitive Cell Death in Arabidopsis

“…Therefore, conversion from soluble to lipid bound ATG8, as well as subcellular localization of green fluorescent protein (GFP) fused protein, have been used to monitor the occurrence of autophagy . Plants have a complement of autophagy proteins, and loss-of-function mutations in ATG genes such as ATG9, ATG7, ATG5, and ATG4a/b indicate that autophagy is central to plant source-sink relations and senescence (Thompson et al, 2005;Bassham et al, 2006).…”