Poster: Temperature Responses

Abs # 197: Genetically altered expression of vis1, a small heat shock protein, modifies quality attributes in transgenic tomato fruit

Presenter:	Handa, Avtar K, handa@hort.purdue.edu
Authors	Handa, Avtar K (A)   Deng, Zhiping  (A)
Affiliations:	(A): Department of Horticulture and Landscape Architecture, Purdue Univ, 625 Agriculture Mall Drive West Lafayette, IN 47907

We have recently identified a novel ripening regulated small heat shock gene, vis1, which modifies pectin depolymerization and juice thickness in tomato fruit (Ramakrishna, et al., 2003, Plant Physiol 131:725-736). To establish molecular function of vis1, transgenic tomato lines expressing sense and antisense transcripts of vis1 under the control of CaMV 35S promoter were created. Several independent transgenic plants were selfed and lines homozygous for the introduced genes were selected and characterized. The sense transgenic lines showed vis1 expression in all tissues as determined by Northern and Western blotting under both normal and heat stress conditions. However, accumulation of vis1 transcripts in several antisense lines was impaired even under high temperature conditions. The growth characteristics of both sense and antisense transgenic lines were similar to those of wild type and azygous lines in field. Some decrease in thermo-tolerance, as determined with ion leakage, was observed in transgenic seedlings with attenuated vis1 expression. The ectopic expression of vis1 significantly enhanced juice viscosity, including Bostwick flow and precipitate weight ratio. On the other hand, impaired expression of vis1 resulted in significantly lowered juice viscosity in several independent transgenic lines. Effects of modified vis1 expression on various ripening parameters are being examined. Also, experiments are in progress to determine the mechanism by which vis1 influences fruit ripening attributes. This research was supported by the USDA/NRI grant 94-37304-1110 and BARD grant US-3132-99.