Stay-green protein, defective in Mendel’s green cotyledon mutant, acts independent and upstream of pheophorbide a oxygenase in the chlorophyll catabolic pathway

Aubry, Sylvain; Mani, Jan; Hörtensteiner, Stefan

doi:10.1007/s11103-008-9314-8

Cited by 96 publications

(92 citation statements)

References 53 publications

(122 reference statements)

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“…This surprising finding indicates that the role of SGR may go beyond its requirement for Chl breakdown; it possibly could have a more general role in nitrogen remobilization, maybe by recruiting proteases for the degradation of protein (complexes) during senescence. In line with this is the fact that all SGR mutants analyzed so far, retain high levels of LHCII subunits (Aubry et al 2008;Jiang et al 2007) and a role of SGR in destabilizing Chl-binding protein complexes as a prerequisite for the subsequent degradation of apoproteins and Chl has been suggested (Park et al 2007;Hörtensteiner 2009). In Arabidopsis, levels of SGR were shown to positively correlate with the extent of development of disease or hypersensitive response symptoms during Pseudomonas syringae infections (Mur et al 2010;Mecey et al 2011) and phototoxic Pheide a was considered to contribute to cell death execution (Mur et al 2010).…”

Section: The Stay-green Proteinmentioning

confidence: 68%

Update on the biochemistry of chlorophyll breakdown

2012

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In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multi-step pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past. Abstract In land plants, chlorophyll is broken down to colorless linear tetrapyrroles in a highly conserved multistep pathway. The pathway is termed the 'PAO pathway', because the opening of the chlorine macrocycle present in chlorophyll catalyzed by pheophorbide a oxygenase (PAO), the key enzyme of the pathway, provides the characteristic structural basis found in all further downstream chlorophyll breakdown products. To date, most of the biochemical steps of the PAO pathway have been elucidated and genes encoding many of the chlorophyll catabolic enzymes been identified. This review summarizes the current knowledge on the biochemistry of the PAO pathway and provides insight into recent progress made in the field that indicates that the pathway is more complex than thought in the past.

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Section: The Stay-green Proteinmentioning

confidence: 68%

Update on the biochemistry of chlorophyll breakdown

2012

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“…Lack of PaO is known to result in light-dependent accelerated cell death phenotypes due to accumulation of catabolites in the chl-degradation pathway that are phototoxic (20)(21)(22)(23). In the leaf, SGR1 functions upstream of PaO as sgr1 mutants do not accumulate any phototoxic catabolites that accumulate in pao mutants (14). This model of SGR1 functioning upstream of PaO would explain the viability of mature sgr1-1/sgr2-2 green seed phenotype.…”

Section: Discussionmentioning

confidence: 98%

“…We hypothesized that if lack of ABI3 function results in the embryo stay-green phenotype, then the expression of downstream ABI3 targets will be affected and the factors responsible for embryo-degreening should represent a subset of the targets regulated by ABA. To examine this, we performed microarray analyses to identify the transcriptome profile of embryos in their late maturation phase (13 DAF) when embryos begin to enter the degreening phase (13)(14)(15)(16) and when ABI3 expression is maximal (SI Appendix, Fig. S1C).…”

Section: Abi3-6mentioning

confidence: 99%

“…In Arabidopsis, there are two SGR genes, SGR1 (At4g22920) and SGR2 (At4g11910). Loss-of-function null mutations in the SGR1 did not result in green embryos, although a stay-green vegetative leaf phenotype was reported (13,14). It still remains unexplored whether the Arabidopsis SGR orthologs participate in the seed degreening process similar to Mendel's I locus.…”

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ABI3 controls embryo degreening through Mendel'sIlocus

Delmas

Sankaranarayanan

Deb

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

141

153

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Chlorophyll (chl) is essential for light capture and is the starting point that provides the energy for photosynthesis and thus plant growth. Obviously, for this reason, retention of the green chlorophyll pigment is considered a desirable crop trait. However, the presence of chlorophyll in mature seeds can be an undesirable trait that can affect seed maturation, seed oil quality, and meal quality. Occurrence of mature green seeds in oil crops such as canola and soybean due to unfavorable weather conditions during seed maturity is known to cause severe losses in revenue. One recently identified candidate that controls the chlorophyll degradation machinery is the stay-green gene, SGR1 that was mapped to Mendel's I locus responsible for cotyledon color (yellow versus green) in peas. A defect in SGR1 leads to leaf stay-green phenotypes in Arabidopsis and rice, but the role of SGR1 in seed degreening and the signaling machinery that converges on SGR1 have remained elusive. To decipher the gene regulatory network that controls degreening in Arabidopsis, we have used an embryo staygreen mutant to demonstrate that embryo degreening is achieved by the SGR family and that this whole process is regulated by the phytohormone abscisic acid (ABA) through ABSCISIC ACID INSEN-SITIVE 3 (ABI3); a B3 domain transcription factor that has a highly conserved and essential role in seed maturation, conferring desiccation tolerance. Misexpression of ABI3 was sufficient to rescue cold-induced green seed phenotype in Arabidopsis. This finding reveals a mechanistic role for ABI3 during seed degreening and thus targeting of this pathway could provide a solution to the green seed problem in various oil-seed crops.freezing tolerance | nondormant T he success of angiosperms impinges on their ability to desiccate and protect their embryos in a dormant state until favorable conditions are perceived. In many angiosperms and oilseed plants such as Arabidopsis and canola, this desiccation process during seed maturation is intricately coupled to loss of chlorophyll (chl) from photosynthetically active embryos (1). During the embryo maturation phase, as the embryos begin to lose their chlorophyll, they concomitantly initiate the process of acquisition of desiccation tolerance and dormancy, thereby producing mature, brown (degreened) and dormant seeds. The persistence of chlorophyll in mature seeds has negative impacts on seed storability in many commercial plant species such as canola, cabbage, carrot, geranium, and soybean (2-4). Apart from contributing to reduced storability, prevalence of green seeds in mature oil seeds (canola and soybean) is also associated with reduced shelf life of oil and production of unfavorable odors and flavors. Particularly, in canola, which is one of the major global cash crops, the frost-induced green seed problem has been estimated to result in an annual loss of $150 million in revenue in North America alone (5, 6).During seed development, abscisic acid (ABA) is known to control mid to late stages of embryo maturation...

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“…FW, Fresh weight; WT, wild type. steps upstream of dephytylation, such as SGR and NYC1 (that is, a CCE involved in chlorophyll b-to-chlorophyll a reduction), also result in stay-greenness coupled to apoprotein retention (Kusaba et al, 2007;Park et al, 2007;Aubry et al, 2008;Barry et al, 2008;Horie et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Different Mechanisms Are Responsible for Chlorophyll Dephytylation during Fruit Ripening and Leaf Senescence in Tomato

et al. 2014

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Chlorophyll breakdown occurs in different green plant tissues (e.g. during leaf senescence and in ripening fruits). For different plant species, the PHEOPHORBIDE A OXYGENASE (PAO)/phyllobilin pathway has been described to be the major chlorophyll catabolic pathway. In this pathway, pheophorbide (i.e. magnesium-and phytol-free chlorophyll) occurs as a core intermediate. Most of the enzymes involved in the PAO/phyllobilin pathway are known; however, the mechanism of dephytylation remains uncertain. During Arabidopsis (Arabidopsis thaliana) leaf senescence, phytol hydrolysis is catalyzed by PHEOPHYTINASE (PPH), which is specific for pheophytin (i.e. magnesium-free chlorophyll). By contrast, in fruits of different Citrus spp., chlorophyllase, hydrolyzing phytol from chlorophyll, was shown to be active. Here, we enlighten the process of chlorophyll breakdown in tomato (Solanum lycopersicum), both in leaves and fruits. We demonstrate the activity of the PAO/phyllobilin pathway and identify tomato PPH (SlPPH), which, like its Arabidopsis ortholog, was specifically active on pheophytin. SlPPH localized to chloroplasts and was transcriptionally up-regulated during leaf senescence and fruit ripening. SlPPH-silencing tomato lines were impaired in chlorophyll breakdown and accumulated pheophytin during leaf senescence. However, although pheophytin transiently accumulated in ripening fruits of SlPPH-silencing lines, ultimately these fruits were able to degrade chlorophyll like the wild type. We conclude that PPH is the core phytol-hydrolytic enzyme during leaf senescence in different plant species; however, fruit ripening involves other hydrolases, which are active in parallel to PPH or are the core hydrolases in fruits. These hydrolases remain unidentified, and we discuss the question of whether chlorophyllases might be involved.

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Stay-green protein, defective in Mendel’s green cotyledon mutant, acts independent and upstream of pheophorbide a oxygenase in the chlorophyll catabolic pathway

Cited by 96 publications

References 53 publications

Update on the biochemistry of chlorophyll breakdown

Update on the biochemistry of chlorophyll breakdown

ABI3 controls embryo degreening through Mendel'sIlocus

Different Mechanisms Are Responsible for Chlorophyll Dephytylation during Fruit Ripening and Leaf Senescence in Tomato

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