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Monogalactosyldiacylglycerol synthesis in the outer envelope membrane of chloroplasts is required for enhanced growth under sucrose supplementation.

Murakawa M, Shimojima M, Shimomura Y, Kobayashi K, Awai K, Ohta H - Front Plant Sci (2014)

Bottom Line: Sucrose supplementation retarded the growth of the Arabidopsis MGD3 knockout mutant mgd3 but enhanced the growth of transgenic Arabidopsis plants overexpressing MGD3 compared with wild type, indicating the involvement of MGD3 in plant growth under sucrose-replete conditions.Although most features such as chlorophyll content, photosynthetic activity, and Pi content were comparable between wild-type and the transgenic plants overexpressing MGD3, sucrose content in shoot tissues decreased and incorporation of exogenously supplied carbon to DGDG was enhanced in the MGD3-overexpressing plants compared with wild type.Our results suggest that MGD3 plays an important role in supplying DGDG as a component of extraplastidial membranes to support enhanced plant growth under conditions of carbon excess.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Biological Sciences, Tokyo Institute of Technology Yokohama, Japan.

ABSTRACT
Plant galactolipid synthesis on the outer envelope membranes of chloroplasts is an important biosynthetic pathway for sustained growth under conditions of phosphate (Pi) depletion. During Pi starvation, the amount of digalactosyldiacylglycerol (DGDG) is increased to substitute for the phospholipids that are degraded for supplying Pi. An increase in DGDG concentration depends on an adequate supply of monogalactosyldiacylglycerol (MGDG), which is a substrate for DGDG synthesis and is synthesized by a type-B MGDG synthase, MGD3. Recently, sucrose was suggested to be a global regulator of plant responses to Pi starvation. Thus, we analyzed expression levels of several genes involved in lipid remodeling during Pi starvation in Arabidopsis thaliana and found that the abundance of MGD3 mRNA increased when sucrose was exogenously supplied to the growth medium. Sucrose supplementation retarded the growth of the Arabidopsis MGD3 knockout mutant mgd3 but enhanced the growth of transgenic Arabidopsis plants overexpressing MGD3 compared with wild type, indicating the involvement of MGD3 in plant growth under sucrose-replete conditions. Although most features such as chlorophyll content, photosynthetic activity, and Pi content were comparable between wild-type and the transgenic plants overexpressing MGD3, sucrose content in shoot tissues decreased and incorporation of exogenously supplied carbon to DGDG was enhanced in the MGD3-overexpressing plants compared with wild type. Our results suggest that MGD3 plays an important role in supplying DGDG as a component of extraplastidial membranes to support enhanced plant growth under conditions of carbon excess.

No MeSH data available.


Related in: MedlinePlus

Fresh weight of WT and the mgd3 mutant under conditions with or without exogenously supplied sucrose. Plants grown on MS medium supplemented with +suc or −suc for 7 d were then transferred to ½MS agar with or without sucrose, respectively, and grown for another 7 d. (A) Shoot fresh weight. (B) Root fresh weight. Values represent the mean ± SE from shoots and roots (n = 12 each). *P < 0.05.
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Figure 2: Fresh weight of WT and the mgd3 mutant under conditions with or without exogenously supplied sucrose. Plants grown on MS medium supplemented with +suc or −suc for 7 d were then transferred to ½MS agar with or without sucrose, respectively, and grown for another 7 d. (A) Shoot fresh weight. (B) Root fresh weight. Values represent the mean ± SE from shoots and roots (n = 12 each). *P < 0.05.

Mentions: Supplementation of growth medium with sucrose promotes plant growth (Karthikeyan et al., 2007). To clarify whether type-B MGDG synthases are involved in the growth enhancement observed under sucrose supplementation, fresh weight of shoots and roots of a MGD3 knockout mutant (mgd3) (Kobayashi et al., 2009a) was compared with that of WT (Figure 2). Without sucrose supplementation, the fresh weight of roots and shoots of mgd3 was similar to that of WT (Figures 2A,B). When sucrose was supplied, however, fresh weight of shoot and root of mgd3 was ~10 and ~14% lower compared with WT, respectively (Figures 2A,B). These data indicated that MGD3 plays a role in seedling growth under sucrose supplementation.


Monogalactosyldiacylglycerol synthesis in the outer envelope membrane of chloroplasts is required for enhanced growth under sucrose supplementation.

Murakawa M, Shimojima M, Shimomura Y, Kobayashi K, Awai K, Ohta H - Front Plant Sci (2014)

Fresh weight of WT and the mgd3 mutant under conditions with or without exogenously supplied sucrose. Plants grown on MS medium supplemented with +suc or −suc for 7 d were then transferred to ½MS agar with or without sucrose, respectively, and grown for another 7 d. (A) Shoot fresh weight. (B) Root fresh weight. Values represent the mean ± SE from shoots and roots (n = 12 each). *P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4066442&req=5

Figure 2: Fresh weight of WT and the mgd3 mutant under conditions with or without exogenously supplied sucrose. Plants grown on MS medium supplemented with +suc or −suc for 7 d were then transferred to ½MS agar with or without sucrose, respectively, and grown for another 7 d. (A) Shoot fresh weight. (B) Root fresh weight. Values represent the mean ± SE from shoots and roots (n = 12 each). *P < 0.05.
Mentions: Supplementation of growth medium with sucrose promotes plant growth (Karthikeyan et al., 2007). To clarify whether type-B MGDG synthases are involved in the growth enhancement observed under sucrose supplementation, fresh weight of shoots and roots of a MGD3 knockout mutant (mgd3) (Kobayashi et al., 2009a) was compared with that of WT (Figure 2). Without sucrose supplementation, the fresh weight of roots and shoots of mgd3 was similar to that of WT (Figures 2A,B). When sucrose was supplied, however, fresh weight of shoot and root of mgd3 was ~10 and ~14% lower compared with WT, respectively (Figures 2A,B). These data indicated that MGD3 plays a role in seedling growth under sucrose supplementation.

Bottom Line: Sucrose supplementation retarded the growth of the Arabidopsis MGD3 knockout mutant mgd3 but enhanced the growth of transgenic Arabidopsis plants overexpressing MGD3 compared with wild type, indicating the involvement of MGD3 in plant growth under sucrose-replete conditions.Although most features such as chlorophyll content, photosynthetic activity, and Pi content were comparable between wild-type and the transgenic plants overexpressing MGD3, sucrose content in shoot tissues decreased and incorporation of exogenously supplied carbon to DGDG was enhanced in the MGD3-overexpressing plants compared with wild type.Our results suggest that MGD3 plays an important role in supplying DGDG as a component of extraplastidial membranes to support enhanced plant growth under conditions of carbon excess.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Biological Sciences, Tokyo Institute of Technology Yokohama, Japan.

ABSTRACT
Plant galactolipid synthesis on the outer envelope membranes of chloroplasts is an important biosynthetic pathway for sustained growth under conditions of phosphate (Pi) depletion. During Pi starvation, the amount of digalactosyldiacylglycerol (DGDG) is increased to substitute for the phospholipids that are degraded for supplying Pi. An increase in DGDG concentration depends on an adequate supply of monogalactosyldiacylglycerol (MGDG), which is a substrate for DGDG synthesis and is synthesized by a type-B MGDG synthase, MGD3. Recently, sucrose was suggested to be a global regulator of plant responses to Pi starvation. Thus, we analyzed expression levels of several genes involved in lipid remodeling during Pi starvation in Arabidopsis thaliana and found that the abundance of MGD3 mRNA increased when sucrose was exogenously supplied to the growth medium. Sucrose supplementation retarded the growth of the Arabidopsis MGD3 knockout mutant mgd3 but enhanced the growth of transgenic Arabidopsis plants overexpressing MGD3 compared with wild type, indicating the involvement of MGD3 in plant growth under sucrose-replete conditions. Although most features such as chlorophyll content, photosynthetic activity, and Pi content were comparable between wild-type and the transgenic plants overexpressing MGD3, sucrose content in shoot tissues decreased and incorporation of exogenously supplied carbon to DGDG was enhanced in the MGD3-overexpressing plants compared with wild type. Our results suggest that MGD3 plays an important role in supplying DGDG as a component of extraplastidial membranes to support enhanced plant growth under conditions of carbon excess.

No MeSH data available.


Related in: MedlinePlus