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ABSTRACT FROM PLANT CANADA 2005 - Enhancing growth and seed yield in canola by suppression of deoxyhypuysine synthase expression via vacuum-infiltration of Agrobacterium

WANG, T-W., WU, W.Y., ZHANG, C-G,

NOWACK, L.M., THOMPSON, J.E.

Dept of Biology, Univ of Waterloo, Waterloo,

Ontario, Canada N2L 3G1

A full-length cDNA clone encoding canola (Brassica napus cv Westar) deoxyhypusine synthase (DHS) was isolated from a CDNA expression library prepared from senescing leaves. DHS mediates the first of two enzymatic reactions that convert inactive eukaryotic translation initiation factor-5A (eIF-5A) to an activated form, thought to facilitate selective mRNA transportation from the nucleus to the cytoplasm. Transgenic canola seeds expressing the antisense 3?-UTR canola DHS cDNA under regulation of the constitutive cauliflower mosaic virus 35S (CaMV-35S) were obtained by vacuum infiltration of canola inflorescences by modifying the protocol developed for Arabidopsis. The efficiency of transformation was enhanced by removal of new flowers that formed after the plants had been vacuum-infiltrated, and transformation rates of 50 to 60% were routinely obtained. Transgenic plants had reduced levels of leaf DHS protein and exhibited delayed natural leaf senescence. Suppression of DHS also increased leaf size by 1.5- to 2-fold and resulted in increases in seed yield of up to 65%. This was attributable in part to an increase in the size of the siliques, which were on average 18% to 26% longer than wild-type siliques depending on the line. When wild-type and transgenic plants were grown in 6-inch pots, the increase in seed yield accruing from suppression of DHS was ~4.5-fold greater than when the plants were grown in 12 inch pots. Thus suppression of DHS appears to ameliorate the effects of sub-lethal stress engendered by growth in small containers. The increase in seed yield for transgenic plants translates into a corresponding increase in seed oil content based on measurements of triacylglycerol, and there was no change in the fatty acid composition of the oil in transgenic seeds.