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An Arabidopsis mitochondria-localized RRL protein mediates abscisic acid signal transduction through mitochondrial retrograde regulation involving ABI4.

Yao X, Li J, Liu J, Liu K - J. Exp. Bot. (2015)

Bottom Line: High expression levels of RRL were found in germinating seeds and developing seedlings, as revealed by β-glucuronidase (GUS) staining of ProRRL-GUS transgenic lines.The analyses of the structure and function of mitochondria in the knockout rrl mutant showed that the disruption of RRL causes extensively internally vacuolated mitochondria and reduced ABA-stimulated reactive oxygen species (ROS) production.Furthermore, the results revealed that ABI4 is a downstream regulatory factor in RRL-mediated ABA signalling in seed germination and seedling growth.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.

No MeSH data available.


Expression levels of mitochondria-associated genes and ABA-responsive genes in the RRL loss-of-function mutant and overexpression line. The expression levels of some mitochondria-associated and ABA-responsive genes were assayed by quantitative RT-PCR with 5-day-old seedlings of Col-0, rrl, and OE-4. –ABA, ABA-free treatment; +ABA, 50 μM ABA treatment. Gene expression levels were analysed as relative units, with that of ABA-free treated Col-0 plants being taken as 1. Values are the means ±SE of three independent experiments.
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Figure 6: Expression levels of mitochondria-associated genes and ABA-responsive genes in the RRL loss-of-function mutant and overexpression line. The expression levels of some mitochondria-associated and ABA-responsive genes were assayed by quantitative RT-PCR with 5-day-old seedlings of Col-0, rrl, and OE-4. –ABA, ABA-free treatment; +ABA, 50 μM ABA treatment. Gene expression levels were analysed as relative units, with that of ABA-free treated Col-0 plants being taken as 1. Values are the means ±SE of three independent experiments.

Mentions: The requirement for RRL for maintaining the structure and function of mitochondria (Fig. 5) prompted an assay of the expression of mtETC-associated genes including AOX1a, NDB4, CCB452, and NAD2 to be carried out. An isoform of alternative oxidase AOX1a functions as a non-phosphorylating bypass of mitochondrial electron transport, and NDB4 is a alternative type II NAD(P)H dehydrogenase without proton translocation activity in the alternative respiratory pathway (Melo et al., 2004). CCB452 is associated with biogenesis of cytochrome c (van Dongen et al., 2011) and NAD2 encodes a subunit of NAD(P)H dehydrogenase in mitochondrial respiratory chain complex I (Heazlewood et al., 2003). Expression levels of genes were quantitatively analysed after the 5-day-old seedlings were subjected to ABA for 6h (Fig. 6). The expression of mtETC-associated genes including CCB45, NDB4, and NAD2 was not altered by disruption or overexpression of RRL in both the absence and presence of the ABA treatments, except for AOX1a (Fig. 6). In this report, ABA-induced expression of AOX1a was found in Col-0 plants as described previouly (Giraud et al., 2009). It should be noted that AOX1a expression was increased in the rrl mutant in the absence of the ABA treatments, but the ABA induction was affected by mutation of RRL. Overexpression of RRL significantly enhanced the expression level of AOX1a in response to ABA (Fig. 6). Because AOX1a induction also serves as a marker of mitochondrial retrograde responses in Arabidopsis (Rhoads and Subbaiah, 2007), this result suggests that RRL is involved in the retrograde signalling between the mitochondria and nucleus in response to ABA.


An Arabidopsis mitochondria-localized RRL protein mediates abscisic acid signal transduction through mitochondrial retrograde regulation involving ABI4.

Yao X, Li J, Liu J, Liu K - J. Exp. Bot. (2015)

Expression levels of mitochondria-associated genes and ABA-responsive genes in the RRL loss-of-function mutant and overexpression line. The expression levels of some mitochondria-associated and ABA-responsive genes were assayed by quantitative RT-PCR with 5-day-old seedlings of Col-0, rrl, and OE-4. –ABA, ABA-free treatment; +ABA, 50 μM ABA treatment. Gene expression levels were analysed as relative units, with that of ABA-free treated Col-0 plants being taken as 1. Values are the means ±SE of three independent experiments.
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Related In: Results  -  Collection

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Figure 6: Expression levels of mitochondria-associated genes and ABA-responsive genes in the RRL loss-of-function mutant and overexpression line. The expression levels of some mitochondria-associated and ABA-responsive genes were assayed by quantitative RT-PCR with 5-day-old seedlings of Col-0, rrl, and OE-4. –ABA, ABA-free treatment; +ABA, 50 μM ABA treatment. Gene expression levels were analysed as relative units, with that of ABA-free treated Col-0 plants being taken as 1. Values are the means ±SE of three independent experiments.
Mentions: The requirement for RRL for maintaining the structure and function of mitochondria (Fig. 5) prompted an assay of the expression of mtETC-associated genes including AOX1a, NDB4, CCB452, and NAD2 to be carried out. An isoform of alternative oxidase AOX1a functions as a non-phosphorylating bypass of mitochondrial electron transport, and NDB4 is a alternative type II NAD(P)H dehydrogenase without proton translocation activity in the alternative respiratory pathway (Melo et al., 2004). CCB452 is associated with biogenesis of cytochrome c (van Dongen et al., 2011) and NAD2 encodes a subunit of NAD(P)H dehydrogenase in mitochondrial respiratory chain complex I (Heazlewood et al., 2003). Expression levels of genes were quantitatively analysed after the 5-day-old seedlings were subjected to ABA for 6h (Fig. 6). The expression of mtETC-associated genes including CCB45, NDB4, and NAD2 was not altered by disruption or overexpression of RRL in both the absence and presence of the ABA treatments, except for AOX1a (Fig. 6). In this report, ABA-induced expression of AOX1a was found in Col-0 plants as described previouly (Giraud et al., 2009). It should be noted that AOX1a expression was increased in the rrl mutant in the absence of the ABA treatments, but the ABA induction was affected by mutation of RRL. Overexpression of RRL significantly enhanced the expression level of AOX1a in response to ABA (Fig. 6). Because AOX1a induction also serves as a marker of mitochondrial retrograde responses in Arabidopsis (Rhoads and Subbaiah, 2007), this result suggests that RRL is involved in the retrograde signalling between the mitochondria and nucleus in response to ABA.

Bottom Line: High expression levels of RRL were found in germinating seeds and developing seedlings, as revealed by β-glucuronidase (GUS) staining of ProRRL-GUS transgenic lines.The analyses of the structure and function of mitochondria in the knockout rrl mutant showed that the disruption of RRL causes extensively internally vacuolated mitochondria and reduced ABA-stimulated reactive oxygen species (ROS) production.Furthermore, the results revealed that ABI4 is a downstream regulatory factor in RRL-mediated ABA signalling in seed germination and seedling growth.

View Article: PubMed Central - PubMed

Affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.

No MeSH data available.