The Mechanism of Variegation in immutans Provides Insight into Chloroplast Biogenesis

Foudree, Andrew; Putarjunan, Aarthi; Sekhar, Kondapalli Venkata Gowri Chandra; Nolan, Trevor M.; Fussell, Jenna; Pogorelko, Gennady; Rodermel, Steven R.

doi:10.3389/fpls.2012.00260

Cited by 54 publications

(44 citation statements)

References 114 publications

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“…However, it does not necessarily mean that these parts of the leaves are devoid of these pigments. They may contain extremely low concentrations of Car (below detection limit) or/and colourless Car such as phytoene that was found in white sectors of variegated Arabidopsis thaliana mutants (Wetzel et al 1994, Wu et al 1999, Foudree et al 2012.…”

Section: Discussionmentioning

confidence: 99%

Photosynthetic activity of variegated leaves of Coleus × hybridus hort. cultivars characterised by chlorophyll fluorescence techniques

2016

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Different pigments often occur together and affect photosynthetic characteristics of the respective leaf portions. In this study, photosynthetic activity in variegated leaves of five cultivars of the ornamental and medicinal plant, Coleus × hybridus hort., was estimated by image analysis and point data measurements of major chlorophyll (Chl) fluorescence parameters and related to the amount of photosynthetic pigments measured with a Chl meter or spectrophotometrically in leaf extracts. Significant differences in Chl and carotenoid (Car) contents were noticed among differentially pigmented sectors of a leaf and among the cultivars. Although the higher Chl concentration was noticed in purple parts compared to green parts of the leaves, the values of minimal and maximal fluorescence yield at the dark-and light-adapted state (F0, F m , F 0 ', F m ', respectively) were a little lower than those in the green sectors, indicating photoprotective effects provided by anthocyanins and Car, more abundant in the red parts. The lowest Chl and Car content was detected in creamy-yellow and pink sectors and this contributed to low F 0 , F m , and F m ', maximal quantum yield of PSII photochemistry, and nonphotochemical and photochemical quenching but high PSII maximum efficiency and effective quantum yield of PSII photochemistry. Both methods of Chl fluorescence analysis revealed heterogeneity in capture, transfer, and dissipation of excitation energy but Chl fluorescence imaging was more suitable in examining very narrow pigmented leaf areas.

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Section: Discussionmentioning

confidence: 99%

Photosynthetic activity of variegated leaves of Coleus × hybridus hort. cultivars characterised by chlorophyll fluorescence techniques

2016

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“…In addition to linear electron transport, PTOX activity can be coupled to other processes that feed electrons to the PQ pool, including chlororespiration, cyclic electron flow around PSI, and the two desaturation steps of carotenoid biosynthesis catalyzed by phytoene desaturase and z-carotene desaturase (Albrecht et al, 1995;Peltier and Cournac, 2002;Okegawa et al, 2010;Putarjunan et al, 2013). It can also act as a safety valve to dissipate excess absorbed energy, thereby preventing the overreduction of photosynthetic electron carriers and protecting PSI and PSII from photoinhibition (McDonald et al, 2011;Foudree et al, 2012;Putarjunan et al, 2013). In the absence of PTOX, developing thylakoids become overreduced and phytoene accumulates, either because of a decreased supply of PQ available to phytoene desaturase and/or because electron transfer from phytoene to an overreduced PQ pool is not energetically favorable (Shahbazi et al, 2007;Rosso et al, 2009).…”

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confidence: 99%

“…; Liu et al, 2010;Foudree et al, 2012;Putarjunan et al, 2013). These studies have included the characterization of second-site suppressors that rescue the variegation phenotype of im, producing all-green plants.…”

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confidence: 99%

giganteaSuppressesimmutansVariegation by Interactions with Cytokinin and Gibberellin Signaling Pathways

Putarjunan

Rodermel

2014

Plant Physiology

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The immutans (im) variegation mutant of Arabidopsis (Arabidopsis thaliana) is an ideal model to gain insight into factors that control chloroplast biogenesis. im defines the gene for PTOX, a plastoquinol terminal oxidase that participates in the control of thylakoid redox. Here, we report that the im defect can be suppressed during the late stages of plant development by gigantea (gi2), which defines the gene for GI, a central component of the circadian clock that plays a poorly understood role in diverse plant developmental processes. imgi2 mutants are late flowering and display other well-known phenotypes associated with gi2, such as starch accumulation and resistance to oxidative stress. We show that the restoration of chloroplast biogenesis in imgi2 is caused by a development-specific derepression of cytokinin signaling that involves cross talk with signaling pathways mediated by gibberellin (GA) and SPINDLY (SPY), a GA response inhibitor. Suppression of the plastid defect in imgi2 is likely caused by a relaxation of excitation pressures in developing plastids by factors contributed by gi2, including enhanced rates of photosynthesis and increased resistance to oxidative stress. Interestingly, the suppression phenotype of imgi can be mimicked by crossing im with the starch accumulation mutant, starch excess1 (sex1), perhaps because sex1 utilizes pathways similar to gi. We conclude that our studies provide a direct genetic linkage between GI and chloroplast biogenesis, and we construct a model of interactions between signaling pathways mediated by gi, GA, SPY, cytokinins, and sex1 that are required for chloroplast biogenesis.

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“…The report by Foudree et al (2012) provides an update on PTOX, the mechanism of immutans variegation, and discusses findings pertaining to compensatory mechanisms in the mutant.…”

Section: Progress In Redox-associated Signalingmentioning

confidence: 99%

Retrograde signals galore

Kleine

Leister

2013

Front. Plant Sci.

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The Mechanism of Variegation in immutans Provides Insight into Chloroplast Biogenesis

Cited by 54 publications

References 114 publications

Photosynthetic activity of variegated leaves of Coleus × hybridus hort. cultivars characterised by chlorophyll fluorescence techniques

Photosynthetic activity of variegated leaves of Coleus × hybridus hort. cultivars characterised by chlorophyll fluorescence techniques

giganteaSuppressesimmutansVariegation by Interactions with Cytokinin and Gibberellin Signaling Pathways

Retrograde signals galore

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