Poster: Late and Moved Abstracts

Abs # 984: Differential maintenance of photosynthetic capacity under abiotic stresses in trehalose- and LEA protein-producing transgenic plants

Presenter:	Jun, Sung-Soo , ssjun@snu.ac.kr
Authors	Jun, Sung-Soo  (A)   Shin, Min-Kyung  (A)   Choi, Hye Jin  (A)   Lee, Hae Yeon  (A)   Hong, Young-Nam  (A)
Affiliations:	(A): Seoul National University
Web Site:	http://biosci.snu.ac.kr

We demonstrated the effectiveness of trehalose and LEA proteins on enhancing tolerance against drought, high salinity, and heat stress using transgenic tobacco (Nicotiana tabacum L. var SR1) plants overexpressing E. coli trehalose-6-phosphate synthase gene (otsA) or hot pepper (Capsicum annuum) LEA protein gene (CaLEA1). Here we compared their effectiveness on maintaining photosynthetic capacity under those stresses. For trehalose-producing plants, Pmax of O₂ evolution was similarly decreased upon dehydration in both nontransformants and transgenic plants. Contrastingly, in CaLEA1-overexpressing plants, Pmax was significantly less inhibited. No noticeable differences in Chl fluorescence parameters were observed between both transgenic plants and nontransformants. Thus whereas trehalose confers transgenic plants improved water retaining ability against dehydration without maintaining their photosynthetic capacity, LEA proteins extend their effectiveness to preserve photosynthetic capacity. Against high salinity, trehalose-producing plants did not show any improved photosynthetic capacity. In contrast, CaLEA1-overexpressing plants maintained photosynthetic activities somewhat better in term of Pmax, photochemical efficiency of PSII (Fv/Fm), and photochemical activity (qP). Against heat stress, both trehalose-producing and CaLEA1-overexpressing plants maintained photosynthetic activities much better in all aspects of photosynthetic parameters tested, but CaLEA1-overexpressing plants slightly performed better in overall. In summary, while both trehalose and CaLEA1 protein are comparatively effective in enhancing tolerance against dehydration, high salinity, and heat stress, CaLEA1 protein is more effective agent in maintaining photosynthetic capacity under those stresses.