Glycinebetaine enhances the tolerance of tomato plants to high temperature during germination of seeds and growth of seedlings
Shufen Li¹, Feng Li¹, Jianwei Wang¹, Wen Zhang¹, Qingwei Meng¹, Tony HH Chen², Norio Murata³ and Xinghong Yang^1*

¹College of Life Science, State Key Laboratory of Crop Biology, Shandong Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, People’s Republic of China.
²Department of Horticulture, ALS 4017, Oregon State University, Corvallis, OR 97331, USA.
³National Institute for Basic Biology, Okazaki 444-8585, Japan .
*Corresponding author: Tel: (+86538 8246167); E-mail address: xhyang@sdau.edu.cn

Abstract
Tomato (Lycopersicon esculentum cv. ‘Moneymaker’) was transformed with a codA gene, from Arthrobacter globiformis, for choline oxidase that had been modified to allow targeting to both chloroplasts and the cytosol. After incubation at temperatures from 25 ^oC to 55 ^oC for 90 min during imbibition, codA-transgenic seeds germinated faster and at higher frequency than wild-type seeds. After the exposure of imbibed seeds to 40^o/30 ^oC (12 h/12 h) or 34^o/34 ^oC (16 h/8 h), transgenic seeds germinated faster and developed more vigorous seedlings than wild-type seeds. We compared the expression of genes for a mitochondrial small heat-shock protein (MT-sHSP), heat-shock protein 70 (HSP70), and heat shock cognate 70 (HSC70) between wild-type and transgenic seeds after heat stress at 34 ^oC. Levels of expression of all three genes were higher in transgenic seeds than in wild-type seeds during heat stress, and the accumulation of HSP70 was more prominent in codA-transgenic seeds than in wild-type seeds. Our results suggest that GB, either applied exogenously or accumulated in vivo in codA-transgenic seeds, enhanced the expression of heat-shock genes and improved the tolerance to high temperature of tomato seeds during germination.

Key-words: Glycinebetaine; heat-shock protein; high temperature; seed germination; tomato