No abstract

In order to investigate the function of chloroplast ascorbate peroxidase under temperature stress, the thylakoid-bound ascorbate peroxidase gene from tomato leaf (TtAPX) was introduced into tobacco. Transformants were selected for their ability to grow on medium containing kanamycin. RNA gel blot analysis confirmed that TtAPX in tomato was induced by chilling or heat stress. Over-expression of TtAPX in tobacco improved seed germination under temperature stress. Two transgenic tobacco lines showed higher ascorbate peroxidase activity, accumulated less hydrogen peroxide and malondialdehyde than wild type plants under stress condition. The photochemical efficiency of photosystem 2 in the transgenic lines was distinctly higher than that of wild type plants under chilling and heat stresses. Results indicated that the over-expression of TtAPX enhanced tolerance to temperature stress in transgenic tobacco plants.Additional key words: Lycopersicum esculentum, malondialdehyde, Nicotiana tabacum, photosystem 2, thylakoid-bound ascorbate peroxidase, transgenic tobacco.

Ascorbate peroxidase plays a key role in scavenging reactive oxygen species under environmental stresses and in protecting plant cells against toxic effects. The Solanum lycopersicum thylakoid-bound ascorbate peroxidase gene (StAPX) was introduced into tobacco under the control of the cauliflower mosaic virus 35S promoter. Transformants were selected for their ability to grow on medium containing kanamycin. RNA gel blot analysis confirmed that StAPX was transferred into the tobacco genome and StAPX was induced by salt and osmotic stresses in tomato leaves. Over-expression of StAPX in tobacco improved seed germination rate and elevated stress tolerance during post-germination development. Two transgenic lines showed higher APX activity and accumulated less hydrogen peroxide than wild-type plants after stress treatments. The photosynthetic rates, the root lengths, the fresh and dry weights of the transgenic lines were distinctly higher than those of wild-type plants under stress conditions. Results indicated that the over-expression of StAPX had enhanced tolerance to salt stress and osmotic stress in transgenic tobacco plants.

A chloroplast‐localized tomato (Lycopersicon esculentum Mill.) glycerol‐3‐phosphate acyltransferase (LeGPAT) gene was isolated. The antisense tomato plants were got under the control of the caulifower mosaic virus 35S promoter (35S‐CaMV). RNA gel blot analysis confirmed that the expression of LeGPAT was inhibited in the tomato genome. The depletion of LeGPAT caused a massive arrest in pollen development. It also increased the size of tapetal cells, delayed tapetum degeneration, reduced ER membrane biogenesis and altered oil body size. Results therefore suggested that LeGPAT played a crucial role in pollen development. There was, however, no effect on the ovule. The depletion of LeGPAT also increased the saturation of phosphatidylglycerol (PG) fatty acids in thylakoid membranes. Increase of PG‐saturated fatty acids was helpful in alleviating photoinhibition of PSII in tomato plants under heat stress.