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A photorespiratory bypass increases plant growth and seed yield in biofuel crop Camelina sativa.

Dalal J, Lopez H, Vasani NB, Hu Z, Swift JE, Yalamanchili R, Dvora M, Lin X, Xie D, Qu R, Sederoff HW - Biotechnol Biofuels (2015)

Bottom Line: Hydrogenation-derived renewable diesel from camelina is environmentally superior to that from canola due to lower agricultural inputs, and the seed meal is FDA approved for animal consumption.The photorespiratory bypass is an effective approach to increase photosynthetic productivity in camelina.By reducing photorespiratory losses and increasing photosynthetic CO2 fixation rates, transgenic plants show dramatic increases in seed yield.

View Article: PubMed Central - PubMed

Affiliation: Department of Crop Science, North Carolina State University, Campus Box 7287, Raleigh, NC 27695-7287 USA.

ABSTRACT

Background: Camelina sativa is an oilseed crop with great potential for biofuel production on marginal land. The seed oil from camelina has been converted to jet fuel and improved fuel efficiency in commercial and military test flights. Hydrogenation-derived renewable diesel from camelina is environmentally superior to that from canola due to lower agricultural inputs, and the seed meal is FDA approved for animal consumption. However, relatively low yield makes its farming less profitable. Our study is aimed at increasing camelina seed yield by reducing carbon loss from photorespiration via a photorespiratory bypass. Genes encoding three enzymes of the Escherichia coli glycolate catabolic pathway were introduced: glycolate dehydrogenase (GDH), glyoxylate carboxyligase (GCL) and tartronic semialdehyde reductase (TSR). These enzymes compete for the photorespiratory substrate, glycolate, convert it to glycerate within the chloroplasts, and reduce photorespiration. As a by-product of the reaction, CO2 is released in the chloroplast, which increases photosynthesis. Camelina plants were transformed with either partial bypass (GDH), or full bypass (GDH, GCL and TSR) genes. Transgenic plants were evaluated for physiological and metabolic traits.

Results: Expressing the photorespiratory bypass genes in camelina reduced photorespiration and increased photosynthesis in both partial and full bypass expressing lines. Expression of partial bypass increased seed yield by 50-57 %, while expression of full bypass increased seed yield by 57-73 %, with no loss in seed quality. The transgenic plants also showed increased vegetative biomass and faster development; they flowered, set seed and reached seed maturity about 1 week earlier than WT. At the transcriptional level, transgenic plants showed differential expression in categories such as respiration, amino acid biosynthesis and fatty acid metabolism. The increased growth of the bypass transgenics compared to WT was only observed in ambient or low CO2 conditions, but not in elevated CO2 conditions.

Conclusions: The photorespiratory bypass is an effective approach to increase photosynthetic productivity in camelina. By reducing photorespiratory losses and increasing photosynthetic CO2 fixation rates, transgenic plants show dramatic increases in seed yield. Because photorespiration causes losses in productivity of most C3 plants, the bypass approach may have significant impact on increasing agricultural productivity for C3 crops.

No MeSH data available.


Related in: MedlinePlus

Cluster 2B shows transcripts with higher expression levels in DEF2+TG1 compared to DEF lines. The full data set is included in Additional file 1: Table S2 (blue low; yellow high; linear range)
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Fig12: Cluster 2B shows transcripts with higher expression levels in DEF2+TG1 compared to DEF lines. The full data set is included in Additional file 1: Table S2 (blue low; yellow high; linear range)

Mentions: The other interesting transcripts were those that showed differences in abundance between the two transgenic lines expressing either only glycolate dehydrogenase (DEF2) of the full bypass (Full) lines. Cluster 2A shows transcripts with higher abundance in DEF2 lines compared to Full bypass expressing lines (Fig. 12, Additional file 1: Table S2). This cluster is enriched in auxin signaling transcripts (ARF5, ARF5-like, IAA13, auxin transport protein BIG and BIG-like), starch metabolism transcripts (alpha amylase, isoamylase, glucan:water dikinase), several callose synthase isoforms, as well as two almost identical cytoplasmic acetyl-CoA carboxylase 1 transcripts encoding ACCases involved in flavonoid biosynthesis. A chloroplast-like superoxide dismutase also had higher abundance in DEF2 and WT compared to DEF2+TG1 plants.Fig. 12


A photorespiratory bypass increases plant growth and seed yield in biofuel crop Camelina sativa.

Dalal J, Lopez H, Vasani NB, Hu Z, Swift JE, Yalamanchili R, Dvora M, Lin X, Xie D, Qu R, Sederoff HW - Biotechnol Biofuels (2015)

Cluster 2B shows transcripts with higher expression levels in DEF2+TG1 compared to DEF lines. The full data set is included in Additional file 1: Table S2 (blue low; yellow high; linear range)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4625952&req=5

Fig12: Cluster 2B shows transcripts with higher expression levels in DEF2+TG1 compared to DEF lines. The full data set is included in Additional file 1: Table S2 (blue low; yellow high; linear range)
Mentions: The other interesting transcripts were those that showed differences in abundance between the two transgenic lines expressing either only glycolate dehydrogenase (DEF2) of the full bypass (Full) lines. Cluster 2A shows transcripts with higher abundance in DEF2 lines compared to Full bypass expressing lines (Fig. 12, Additional file 1: Table S2). This cluster is enriched in auxin signaling transcripts (ARF5, ARF5-like, IAA13, auxin transport protein BIG and BIG-like), starch metabolism transcripts (alpha amylase, isoamylase, glucan:water dikinase), several callose synthase isoforms, as well as two almost identical cytoplasmic acetyl-CoA carboxylase 1 transcripts encoding ACCases involved in flavonoid biosynthesis. A chloroplast-like superoxide dismutase also had higher abundance in DEF2 and WT compared to DEF2+TG1 plants.Fig. 12

Bottom Line: Hydrogenation-derived renewable diesel from camelina is environmentally superior to that from canola due to lower agricultural inputs, and the seed meal is FDA approved for animal consumption.The photorespiratory bypass is an effective approach to increase photosynthetic productivity in camelina.By reducing photorespiratory losses and increasing photosynthetic CO2 fixation rates, transgenic plants show dramatic increases in seed yield.

View Article: PubMed Central - PubMed

Affiliation: Department of Crop Science, North Carolina State University, Campus Box 7287, Raleigh, NC 27695-7287 USA.

ABSTRACT

Background: Camelina sativa is an oilseed crop with great potential for biofuel production on marginal land. The seed oil from camelina has been converted to jet fuel and improved fuel efficiency in commercial and military test flights. Hydrogenation-derived renewable diesel from camelina is environmentally superior to that from canola due to lower agricultural inputs, and the seed meal is FDA approved for animal consumption. However, relatively low yield makes its farming less profitable. Our study is aimed at increasing camelina seed yield by reducing carbon loss from photorespiration via a photorespiratory bypass. Genes encoding three enzymes of the Escherichia coli glycolate catabolic pathway were introduced: glycolate dehydrogenase (GDH), glyoxylate carboxyligase (GCL) and tartronic semialdehyde reductase (TSR). These enzymes compete for the photorespiratory substrate, glycolate, convert it to glycerate within the chloroplasts, and reduce photorespiration. As a by-product of the reaction, CO2 is released in the chloroplast, which increases photosynthesis. Camelina plants were transformed with either partial bypass (GDH), or full bypass (GDH, GCL and TSR) genes. Transgenic plants were evaluated for physiological and metabolic traits.

Results: Expressing the photorespiratory bypass genes in camelina reduced photorespiration and increased photosynthesis in both partial and full bypass expressing lines. Expression of partial bypass increased seed yield by 50-57 %, while expression of full bypass increased seed yield by 57-73 %, with no loss in seed quality. The transgenic plants also showed increased vegetative biomass and faster development; they flowered, set seed and reached seed maturity about 1 week earlier than WT. At the transcriptional level, transgenic plants showed differential expression in categories such as respiration, amino acid biosynthesis and fatty acid metabolism. The increased growth of the bypass transgenics compared to WT was only observed in ambient or low CO2 conditions, but not in elevated CO2 conditions.

Conclusions: The photorespiratory bypass is an effective approach to increase photosynthetic productivity in camelina. By reducing photorespiratory losses and increasing photosynthetic CO2 fixation rates, transgenic plants show dramatic increases in seed yield. Because photorespiration causes losses in productivity of most C3 plants, the bypass approach may have significant impact on increasing agricultural productivity for C3 crops.

No MeSH data available.


Related in: MedlinePlus