Transformation of a very chilling-sensitive orchid, "Phalenopusis" with Agrobacreium carrying spinach fatty acid desaturase

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Temperature is a major environmental factor governing the distribution of both wild and cultivated plant species. Many economically important plants having tropical or subtropical origins, for example maize, banana, citrus and squash, are injured by exposure to temperatures slightly above the freezing point of their tissues. Lyons and Raison have proposed that chilling injury is primarily caused by the physical response of membrane lipids to low temperature. Recently, Murata proposed that, in chloroplasts of higher plants, phosphatidylglycerol (PG) might be the molecule resposible for the primary event in chilling injury by virtue of its content of molecular species containing saturated fatty acids.Properties of two enzymes, Glycerol-3-phosphate acyltransferase and Stearoyl ACP desaturase (SAD), have been recognized to be very important on synthesis of unsaturated PG species. SAD introduces the first double bond into C18 fatty acids in higher plants and, threfore, it is involved in cotrolling the extent of unsaturation of membrane lipids. We have reported the isolation and characterization of a cDNA clone that encodes a precursor to SAD of spinach young leaf, chilling resistant plant. Then, we tried transformation of chilling sensitive plants, petunia and Phalenopusis, with Agrobacterium tumefaciens carrying pBl 121/SAD which was inserted the spinach cDNA clone. Several transformants of petunia obtained thus have been continued to compare the fatty acid composition of PG and the chilling sensitivity. No transformant of Phalenopusis is obtained at present time.