Induction of a Carbon-Starvation-Related Proteolysis in Whole Maize Plants Submitted to Light/Dark Cycles and to Extended Darkness1

Brouquisse, Renaud; Gaudillère, J.P.; Raymond, Philippe

doi:10.1104/pp.117.4.1281

Cited by 144 publications

(146 citation statements)

References 65 publications

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“…From the time-course analysis of chlorophyll contents, atapg9-1 plants start to show an aberrant phenotype at roughly d 3 after initiation of starvation. This suggests that autophagy was induced within 3 d after transfer, which is in agreement with results from studies on autophagy induction in cultured cells or in whole plants during starvation (Moriyasu and Ohsumi, 1996;Brouquisse et al, 1998).…”

Section: Discussionsupporting

confidence: 90%

“…In rice (Oryza sativa)-, sycamore (Acer pseudoplatanus)-, and tobacco (Nicotiana tabacum)-cultured cells, autophagy is induced by Suc starvation (Chen et al, 1994;Aubert et al, 1996;Moriyasu and Ohsumi, 1996). Net protein degradation is induced by carbon starvation in whole maize (Zea mays) plants, most likely by an autophagic process (Brouquisse et al, 1998). In cultured sycamore cells, double-membrane-bound autophagosomes are formed in the cytoplasm and are eventually expelled into the central vacuole (Aubert et al, 1996).…”

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confidence: 99%

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Leaf Senescence and Starvation-Induced Chlorosis Are Accelerated by the Disruption of an Arabidopsis Autophagy Gene

et al. 2002

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Autophagy is an intracellular process for vacuolar bulk degradation of cytoplasmic components. The molecular machinery responsible for yeast and mammalian autophagy has recently begun to be elucidated at the cellular level, but the role that autophagy plays at the organismal level has yet to be determined. In this study, a genome-wide search revealed significant conservation between yeast and plant autophagy genes. Twenty-five plant genes that are homologous to 12 yeast genes essential for autophagy were discovered. We identified an Arabidopsis mutant carrying a T-DNA insertion within AtAPG9, which is the only ortholog of yeast Apg9 in Arabidopsis (atapg9-1). AtAPG9 is transcribed in every wild-type organ tested but not in the atapg9-1 mutant. Under nitrogen or carbon-starvation conditions, chlorosis was observed earlier in atapg9-1 cotyledons and rosette leaves compared with wild-type plants. Furthermore, atapg9-1 exhibited a reduction in seed set when nitrogen starved. Even under nutrient growth conditions, bolting and natural leaf senescence were accelerated in atapg9-1 plants. Senescence-associated genes SEN1 and YSL4 were up-regulated in atapg9-1 before induction of senescence, unlike in wild type. All of these phenotypes were complemented by the expression of wild-type AtAPG9 in atapg9-1 plants. These results imply that autophagy is required for maintenance of the cellular viability under nutrient-limited conditions and for efficient nutrient use as a whole plant.Protein degradation is an important process in almost every facet of plant physiology and development. In plants, three major degradation pathways have been described: the ubiquitin-dependent pathway and the chloroplast and the vacuolar degradation pathways (for review, see Vierstra, 1996). Among these pathways, vacuolar degradation is assumed to be involved in bulk protein degradation by virtue of the resident proteases in the vacuole. Two types of vacuoles have been described in plants: the storage vacuole and the lytic central vacuole (for review, see Marty, 1999). However, there may be additional vacuole types that await discovery. Protein storage vacuoles are often found in seed tissues and accumulate proteins that are mobilized and used as the main nutrient resource for germination. Most cells in vegetative tissues have a large central vacuole, containing a wide range of proteases in an acidic environment. Substrate proteins must be transported and sequestered into this vacuole for degradation.Autophagy, a ubiquitous eukaryotic process, is responsible for this sequestration. Two types of autophagy have been described, namely macroautophagy and microautophagy (for review, see Klionsky and Ohsumi, 1999). In yeast macroautophagy, a portion of the cytoplasm is first enclosed by a doublemembrane structure, the autophagosome. The outer membrane of the autophagosome then fuses to the vacuolar membrane, so that its inner membrane structure, the autophagic body, is delivered into the vacuolar lumen. The contents of the autophagic body are then digest...

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Section: Discussionsupporting

confidence: 90%

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confidence: 99%

Leaf Senescence and Starvation-Induced Chlorosis Are Accelerated by the Disruption of an Arabidopsis Autophagy Gene

et al. 2002

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“…Proteolytic Activity Measurements-Global endopeptidase activity measurement was adapted from Brouquisse et al (34). One hundred l of clarified extract and 100 l of azocasein (5 mg ml Ϫ1 in 200 mM MES-KOH (pH 6.0)) were incubated for 3 h at 37°C.…”

mentioning

confidence: 99%

Evidence for the Existence in Arabidopsis thaliana of the Proteasome Proteolytic Pathway

Polge

Jaquinod²,

Holzer

et al. 2009

Journal of Biological Chemistry

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103

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Heavy metals are known to generate reactive oxygen species that lead to the oxidation and fragmentation of proteins, which become toxic when accumulated in the cell. In this study, we investigated the role of the proteasome during cadmium stress in the leaves of Arabidopsis thaliana plants. Using biochemical and proteomics approaches, we present the first evidence of an active proteasome pathway in plants. We identified and characterized the peptidases acting sequentially downstream from the proteasome in animal cells as follows: tripeptidyl-peptidase II, thimet oligopeptidase, and leucine aminopeptidase. We investigated the proteasome proteolytic pathway response in the leaves of 6-week-old A. thaliana plants grown hydroponically for 24, 48, and 144 h in the presence or absence of 50 M cadmium. The gene expression and proteolytic activity of the proteasome and the different proteases of the pathway were found to be up-regulated in response to cadmium. In an in vitro assay, oxidized bovine serum albumin and lysozyme were more readily degraded in the presence of 20 S proteasome and tripeptidylpeptidase II than their nonoxidized form, suggesting that oxidized proteins are preferentially degraded by the Arabidopsis 20 S proteasome pathway. These results show that, in response to cadmium, the 20 S proteasome proteolytic pathway is up-regulated at both RNA and activity levels in Arabidopsis leaves and may play a role in degrading oxidized proteins generated by the stress.

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“…These results suggest that root hypoxia leaded to higher protein degradation. Such a process was observed in maize root tips, 43,63 and in tomato fruits 64 and roots 65 under sugar starvation or extended darkness.…”

Section: Plant Development and Biomass Allocationmentioning

confidence: 82%

Prolonged root hypoxia effects on enzymes involved in nitrogen assimilation pathway in tomato plants

Horchani

Aschi‐Smiti²

2010

Plant Signaling & Behavior

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IntroductionPlants grow in a dynamic environment, which frequently imposes constraints on growth and development. Among the adverse environmental factors commonly encountered by land plants, flooding is one of the most significant abiotic stresses. 1 Flooding of the soil can have a tremendous impact on the growth and survival of plants, and thereby on agricultural as well as natural ecosystems. In the last decades considerable progress has been made in our understanding of the mechanisms that enable certain plant species and cultivars to withstand periods with excess soil water or even complete submergence. Much of the research has been carried out with crop plant species, such as Oryza sativa, Zea mays, Trifolium subterraneum and Medicago sativa, 2-5 but wild species originating from wetland habitats have been also used, mostly for comparative studies. 6,7 With transient flooding or irrigation followed by slow drainage, or in natural wetlands, plant roots can become oxygen deficient because of slow transfer of dissolved oxygen in the waterfilled pore space of the soil. The decrease in ambient oxygen may not be, itself or alone, the perceived signal but could trigger metabolic responses, which then initiate the signalling cascade. 8 The immediate consequence of oxygen depletion is the reduction in respiration, thus diminishing ATP generation, and leading to a decrease in the ATP/ADP ratio and the adenylate energy charge. 9 In order to investigate the effects of root hypoxia (1-2% oxygen) on the nitrogen (N) metabolism of tomato plants (Solanum lycopersicum L. cv. Micro-Tom), a range of N compounds and N-assimilating enzymes were performed on roots and leaves of plants submitted to root hypoxia at the second leaf stage for three weeks. Obtained results showed that root hypoxia led to a significant decrease in dry weight (DW) production and nitrate content in roots and leaves. conversely, shoot to root DW ratio and nitrite content were significantly increased. contrary to that in leaves, glutamine synthetase activity was significantly enhanced in roots. The activities of nitrate and nitrite reductase were enhanced in roots as well as leaves. The higher increase in the Nh 4 + content and in the protease activities in roots and leaves of hypoxically treated plants coincide with a greater decrease in soluble protein contents. Taken together, these results suggest that root hypoxia leaded to higher protein degradation. The hypoxia-induced increase in the aminating glutamate dehydrogenase activity may be considered as an alternative N assimilation pathway involved in detoxifying the Nh 4 + , accumulated under hypoxic conditions. With respect to hypoxic stress, the distinct sensitivity of the enzymes involved in N assimilation is discussed. and 0.13 ± 0.03 g, respectively. The changes in the root and shoot dry weights (DW) and in shoot/root ratio were investigated after a three week period of hypoxic treatment. Root hypoxia decreased root and leaf DW production by 34 and 18%, respectively. Shoot to root DW ratio increas...

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Induction of a Carbon-Starvation-Related Proteolysis in Whole Maize Plants Submitted to Light/Dark Cycles and to Extended Darkness1

Cited by 144 publications

References 65 publications

Leaf Senescence and Starvation-Induced Chlorosis Are Accelerated by the Disruption of an Arabidopsis Autophagy Gene

Leaf Senescence and Starvation-Induced Chlorosis Are Accelerated by the Disruption of an Arabidopsis Autophagy Gene

Evidence for the Existence in Arabidopsis thaliana of the Proteasome Proteolytic Pathway

Prolonged root hypoxia effects on enzymes involved in nitrogen assimilation pathway in tomato plants

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