Enhanced cold tolerance in transgenic tobacco expressing a chloroplast omega-3 fatty acid desaturase gene under the control of a cold-inducible promoter.
A new cold-inducible genetic construct was cloned using a chloroplast-specific omega-3-fatty acid desaturase gene (FAD7) under the control of a cold-inducible promoter (cor15a) from Arabidopsis thaliana. RT-PCR confirmed a marked increase in FAD7 expression, in young Nicotiana tabacum (cv. Havana) plants harboring cor15a-FAD7, after a short-term exposure to cold. When young, cold-induced tobacco seedlings were exposed to low-temperature (0.5, 2 or 3.5 degrees C) for up to 44 days, survival within independent cor15a-FAD7 transgenic lines (40.2-96%) was far superior to the wild type (6.7-10.2%). In addition, the major trienoic fatty acid species remained stable in cold-induced cor15a-FAD7 N. tabacum plants under prolonged cold storage while the levels of hexadecatrienoic acid (16:3) and octadecatrienoic acid (18:3) declined in wild type plants under the same conditions (79 and 20.7% respectively). Electron microscopy showed that chloroplast membrane ultrastructure in cor15a-FAD7 transgenic plants was unaffected by prolonged exposure to cold temperatures. In contrast, wild type plants experienced a loss of granal stacking and disorganization of the thylakoid membrane under the same conditions. Changes in membrane integrity coincided with a precipitous decline in leaf chlorophyll concentration and low survival rates in wild type plants. Cold-induced double transgenic N. alata (cv. Domino Mix) plants, harboring both the cor15a-FAD7 cold-tolerance gene and a cor15a-IPT dark-tolerance gene, exhibited dramatically higher survival rates (89-90%) than wild type plants (2%) under prolonged cold storage under dark conditions (2 degrees C for 50 days).
Khodakovskaya
Mariya
M
Plant Science Department, University of Connecticut, Storrs, 06269, USA.
McAvoy
Richard
R
Peters
Jeanne
J
Wu
Hao
H
Li
Yi
Y
D017360:Arabidopsis / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000648:ultrastructure; D003080:Cold Temperature; D018742:DNA, Chloroplast; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008027:Light; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000502:physiology; D011401:Promoter Regions, Genetic; D014026:Nicotiana / Q000235:genetics / Q000502:physiology*
D018742:DNA, Chloroplast; D005227:Fatty Acids; D002734:Chlorophyll; D044943:Fatty Acid Desaturases; C078565:omega-3 fatty acid desaturase