Isolation and functional studies of SAHH gene involved in the regulation of lycopene accumulation in tomato fruit

• Main Authors: Hao-En Ma, 馬浩恩
• Other Authors: Hsu-Liang Hsieh
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/nj285k

碩士 === 國立臺灣大學 === 植物科學研究所 === 106 === Tomato is a famous fruit in the world. It’s not only a fruit, but also a vegetable. Many researchers use it as a model plant to study fruit ripening. Tomato is a climacteric fruit which turns the color of the exocarp from green to red due to ethylene effect. Ethylene participates in the regulation of plant development such as seedling, flowering, fruit. Many factors affect tomato fruit ripening, in which the process of ethylene plays a very important role. TDR4 is a transcription factor of the MADS-box family, which participates in the ripening process of tomato fruit, and can also form complexes with other transcription factors. This complex can regulate ethylene biosynthetic pathway, leading to the regulation of fruit ripening. Besides ethylene, many factors such as other hormones and light may affect fruit ripening. Previous studies showed that gene expressions of TDR4 and SAHH were up-regulated when lycopene accumulation was induced by blue light and red light. In addition to TDR4, the enzyme S-adenosyl-L-homocysteine hydrolase (SAHH) that associates with the SAM cycle may have a potential function to regulate tomato ripening. In my study, I wonder whether SAHH participates in the process of lycopene accumulation and may have a relationship with TDR4. Current results show that TDR4 protein is only expressed in tomato fruit and its levels peaked at the breaker stage. Moreover, there may be protein modification in red ripen stage. SAHH has three homologs in tomato. We examined their gene expressions and indicated that SAHH2 may play an important role in fruit ripening, especially in the breaker stage. Also, SAHH2 may have a regulatory relationship with JRL1 under different light conditions. In addition, the connection between SAHH2, JRL1 and TDR4 remains unclear. We have established SAHH2 overexpression transgenic tomato lines in order to study the regulatory relationship among these three genes. Current evidence reveals that SAHH2 overexpression transgenic lines exhibit curled shapes of leaflets and are sensitive to ethylene. Taken together, this study indicates that SAHH2 not only regulates fruit ripening, but also affects the plant growth and development.