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A High Temperature-Dependent Mitochondrial Lipase EXTRA GLUME1 Promotes Floral Phenotypic Robustness against Temperature Fluctuation in Rice (Oryza sativa L.).

Zhang B, Wu S, Zhang Y, Xu T, Guo F, Tang H, Li X, Wang P, Qian W, Xue Y - PLoS Genet. (2016)

Bottom Line: In this study, we found that eg1 (extra glume1) mutants of rice (Oryza savita L.) showed floral phenotypic variations in different growth locations resulting in a breakdown of floral identity robustness.Furthermore, we found that numerous environmentally responsive genes including many floral identity genes are transcriptionally repressed in eg1 mutants and OsMADS1, OsMADS6 and OsG1 genetically act downstream of EG1 to maintain floral robustness.Collectively, our results demonstrate that EG1 promotes floral robustness against temperature fluctuation by safeguarding the expression of floral identify genes through a high temperature-dependent mitochondrial lipid pathway and uncovers a novel mechanistic insight into floral developmental control.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing, the People's Republic of China.

ABSTRACT
The sessile plants have evolved diverse intrinsic mechanisms to control their proper development under variable environments. In contrast to plastic vegetative development, reproductive traits like floral identity often show phenotypic robustness against environmental variations. However, it remains obscure about the molecular basis of this phenotypic robustness. In this study, we found that eg1 (extra glume1) mutants of rice (Oryza savita L.) showed floral phenotypic variations in different growth locations resulting in a breakdown of floral identity robustness. Physiological and biochemical analyses showed that EG1 encodes a predominantly mitochondria-localized functional lipase and functions in a high temperature-dependent manner. Furthermore, we found that numerous environmentally responsive genes including many floral identity genes are transcriptionally repressed in eg1 mutants and OsMADS1, OsMADS6 and OsG1 genetically act downstream of EG1 to maintain floral robustness. Collectively, our results demonstrate that EG1 promotes floral robustness against temperature fluctuation by safeguarding the expression of floral identify genes through a high temperature-dependent mitochondrial lipid pathway and uncovers a novel mechanistic insight into floral developmental control.

No MeSH data available.


Related in: MedlinePlus

EG1 encodes a functional lipase predominately localized in mitochondria.(a) Co-localization of EG1-GFP or GFP-EG1 fusion protein with mitochondria in rice protoplasts. Mitochondria are marked by dye Mito Tracker Red (MT Red) or MTS-mOrange protein. (b) Localization analysis of EG1-GFP and chloroplasts in rice protoplasts. An EG1-GFP driven by 35S or native promoter is shown in the left and right, respectively. Chloroplasts are detected by its auto-fluorescence. Mitochondria are marked by Mito Tracker Red (MT Red). (c) Localization of mitochondrial (35SPro:COX11-GFP) [60] (up) and cellular (35SPro:GFP) (bottom) controls of rice protoplasts. DIC, pictures photographed by differential interference contrast microscope. Bar = 10 μm. (d) Subcellular fractionation assay. Mit, mitochondria fraction; Chl, chloroplasts fraction; α-FLAG, antibody of FLAG-EG1; α-AOX1/2 and α-COXII, specific antibodies of mitochondrial proteins AOX1/2 and COXII; α-RbcL and α-PsbA, specific antibodies of chloroplast proteins RbcL and PsbA. (e) Lipase activity of EG1 in vitro with P-nPB as a substrate at 30°C. EG1 (Full) and EG1 (Δ45) respectively refer to fusion proteins of full-length or no N-terminal (45 aa) protein of EG1 and SUMO peptide. DGL and pp lipase (porcine pancreatic lipase) were used as positive controls. Values are means ± SE for three independent experiments.
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pgen.1006152.g004: EG1 encodes a functional lipase predominately localized in mitochondria.(a) Co-localization of EG1-GFP or GFP-EG1 fusion protein with mitochondria in rice protoplasts. Mitochondria are marked by dye Mito Tracker Red (MT Red) or MTS-mOrange protein. (b) Localization analysis of EG1-GFP and chloroplasts in rice protoplasts. An EG1-GFP driven by 35S or native promoter is shown in the left and right, respectively. Chloroplasts are detected by its auto-fluorescence. Mitochondria are marked by Mito Tracker Red (MT Red). (c) Localization of mitochondrial (35SPro:COX11-GFP) [60] (up) and cellular (35SPro:GFP) (bottom) controls of rice protoplasts. DIC, pictures photographed by differential interference contrast microscope. Bar = 10 μm. (d) Subcellular fractionation assay. Mit, mitochondria fraction; Chl, chloroplasts fraction; α-FLAG, antibody of FLAG-EG1; α-AOX1/2 and α-COXII, specific antibodies of mitochondrial proteins AOX1/2 and COXII; α-RbcL and α-PsbA, specific antibodies of chloroplast proteins RbcL and PsbA. (e) Lipase activity of EG1 in vitro with P-nPB as a substrate at 30°C. EG1 (Full) and EG1 (Δ45) respectively refer to fusion proteins of full-length or no N-terminal (45 aa) protein of EG1 and SUMO peptide. DGL and pp lipase (porcine pancreatic lipase) were used as positive controls. Values are means ± SE for three independent experiments.

Mentions: Previously, EG1 was shown to be localized in chloroplasts in transient expression assays [54]. However, EG1-like lipases appear to have variable subcellular locations [56–59]. To examine the subcellular localization of EG1 in vivo, two different EG1 and GFP fusion proteins driven by 35S promoter were first expressed in rice protoplasts and were found to be co-localized with both mitochondrial specific dye Mito Tracker Red and mitochondrial maker protein MTS-mOrange [60] but hardly with chloroplast auto-fluorescence, and an EG1-GFP fusion protein driven by native promoter was also detected in mitochondria (Fig 4A and 4B), suggesting that EG1 protein is mainly, if not all, localized in mitochondria. To compare this finding with the previous one, the reported vector pCAMBIA1301-Pro35S:EG1-GFP [54] was also examined in our transient system and a similar localization was detected (S5 Fig). To further verify the EG1 localization, subcellular fractionations of one-week seedlings of eg1-2 complementation lines with FLAG-EG1 (S6 Fig) were successively carried out and the EG1 fusion protein was predominately co-fractionated with mitochondria (Fig 4D), confirming the mitochondrial localization of EG1 in vivo. Taken together, these results showed that EG1 encodes a protein predominately localized in mitochondria. To explore the biochemical function of EG1, we tested its lipase activity [53] in vitro and found that both the full-length EG1 and truncated EG1 without predicted targeting peptides showed significant lipase activity (Fig 4E), indicating that EG1 encodes a functional lipase. Taken together, our results showed that EG1 functions as a predominately mitochondria-localized lipase.


A High Temperature-Dependent Mitochondrial Lipase EXTRA GLUME1 Promotes Floral Phenotypic Robustness against Temperature Fluctuation in Rice (Oryza sativa L.).

Zhang B, Wu S, Zhang Y, Xu T, Guo F, Tang H, Li X, Wang P, Qian W, Xue Y - PLoS Genet. (2016)

EG1 encodes a functional lipase predominately localized in mitochondria.(a) Co-localization of EG1-GFP or GFP-EG1 fusion protein with mitochondria in rice protoplasts. Mitochondria are marked by dye Mito Tracker Red (MT Red) or MTS-mOrange protein. (b) Localization analysis of EG1-GFP and chloroplasts in rice protoplasts. An EG1-GFP driven by 35S or native promoter is shown in the left and right, respectively. Chloroplasts are detected by its auto-fluorescence. Mitochondria are marked by Mito Tracker Red (MT Red). (c) Localization of mitochondrial (35SPro:COX11-GFP) [60] (up) and cellular (35SPro:GFP) (bottom) controls of rice protoplasts. DIC, pictures photographed by differential interference contrast microscope. Bar = 10 μm. (d) Subcellular fractionation assay. Mit, mitochondria fraction; Chl, chloroplasts fraction; α-FLAG, antibody of FLAG-EG1; α-AOX1/2 and α-COXII, specific antibodies of mitochondrial proteins AOX1/2 and COXII; α-RbcL and α-PsbA, specific antibodies of chloroplast proteins RbcL and PsbA. (e) Lipase activity of EG1 in vitro with P-nPB as a substrate at 30°C. EG1 (Full) and EG1 (Δ45) respectively refer to fusion proteins of full-length or no N-terminal (45 aa) protein of EG1 and SUMO peptide. DGL and pp lipase (porcine pancreatic lipase) were used as positive controls. Values are means ± SE for three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4930220&req=5

pgen.1006152.g004: EG1 encodes a functional lipase predominately localized in mitochondria.(a) Co-localization of EG1-GFP or GFP-EG1 fusion protein with mitochondria in rice protoplasts. Mitochondria are marked by dye Mito Tracker Red (MT Red) or MTS-mOrange protein. (b) Localization analysis of EG1-GFP and chloroplasts in rice protoplasts. An EG1-GFP driven by 35S or native promoter is shown in the left and right, respectively. Chloroplasts are detected by its auto-fluorescence. Mitochondria are marked by Mito Tracker Red (MT Red). (c) Localization of mitochondrial (35SPro:COX11-GFP) [60] (up) and cellular (35SPro:GFP) (bottom) controls of rice protoplasts. DIC, pictures photographed by differential interference contrast microscope. Bar = 10 μm. (d) Subcellular fractionation assay. Mit, mitochondria fraction; Chl, chloroplasts fraction; α-FLAG, antibody of FLAG-EG1; α-AOX1/2 and α-COXII, specific antibodies of mitochondrial proteins AOX1/2 and COXII; α-RbcL and α-PsbA, specific antibodies of chloroplast proteins RbcL and PsbA. (e) Lipase activity of EG1 in vitro with P-nPB as a substrate at 30°C. EG1 (Full) and EG1 (Δ45) respectively refer to fusion proteins of full-length or no N-terminal (45 aa) protein of EG1 and SUMO peptide. DGL and pp lipase (porcine pancreatic lipase) were used as positive controls. Values are means ± SE for three independent experiments.
Mentions: Previously, EG1 was shown to be localized in chloroplasts in transient expression assays [54]. However, EG1-like lipases appear to have variable subcellular locations [56–59]. To examine the subcellular localization of EG1 in vivo, two different EG1 and GFP fusion proteins driven by 35S promoter were first expressed in rice protoplasts and were found to be co-localized with both mitochondrial specific dye Mito Tracker Red and mitochondrial maker protein MTS-mOrange [60] but hardly with chloroplast auto-fluorescence, and an EG1-GFP fusion protein driven by native promoter was also detected in mitochondria (Fig 4A and 4B), suggesting that EG1 protein is mainly, if not all, localized in mitochondria. To compare this finding with the previous one, the reported vector pCAMBIA1301-Pro35S:EG1-GFP [54] was also examined in our transient system and a similar localization was detected (S5 Fig). To further verify the EG1 localization, subcellular fractionations of one-week seedlings of eg1-2 complementation lines with FLAG-EG1 (S6 Fig) were successively carried out and the EG1 fusion protein was predominately co-fractionated with mitochondria (Fig 4D), confirming the mitochondrial localization of EG1 in vivo. Taken together, these results showed that EG1 encodes a protein predominately localized in mitochondria. To explore the biochemical function of EG1, we tested its lipase activity [53] in vitro and found that both the full-length EG1 and truncated EG1 without predicted targeting peptides showed significant lipase activity (Fig 4E), indicating that EG1 encodes a functional lipase. Taken together, our results showed that EG1 functions as a predominately mitochondria-localized lipase.

Bottom Line: In this study, we found that eg1 (extra glume1) mutants of rice (Oryza savita L.) showed floral phenotypic variations in different growth locations resulting in a breakdown of floral identity robustness.Furthermore, we found that numerous environmentally responsive genes including many floral identity genes are transcriptionally repressed in eg1 mutants and OsMADS1, OsMADS6 and OsG1 genetically act downstream of EG1 to maintain floral robustness.Collectively, our results demonstrate that EG1 promotes floral robustness against temperature fluctuation by safeguarding the expression of floral identify genes through a high temperature-dependent mitochondrial lipid pathway and uncovers a novel mechanistic insight into floral developmental control.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences and National Center for Plant Gene Research, Beijing, the People's Republic of China.

ABSTRACT
The sessile plants have evolved diverse intrinsic mechanisms to control their proper development under variable environments. In contrast to plastic vegetative development, reproductive traits like floral identity often show phenotypic robustness against environmental variations. However, it remains obscure about the molecular basis of this phenotypic robustness. In this study, we found that eg1 (extra glume1) mutants of rice (Oryza savita L.) showed floral phenotypic variations in different growth locations resulting in a breakdown of floral identity robustness. Physiological and biochemical analyses showed that EG1 encodes a predominantly mitochondria-localized functional lipase and functions in a high temperature-dependent manner. Furthermore, we found that numerous environmentally responsive genes including many floral identity genes are transcriptionally repressed in eg1 mutants and OsMADS1, OsMADS6 and OsG1 genetically act downstream of EG1 to maintain floral robustness. Collectively, our results demonstrate that EG1 promotes floral robustness against temperature fluctuation by safeguarding the expression of floral identify genes through a high temperature-dependent mitochondrial lipid pathway and uncovers a novel mechanistic insight into floral developmental control.

No MeSH data available.


Related in: MedlinePlus