title: Pronounced Phenotypic Changes in Transgenic Tobacco Plants Overexpressing Sucrose Synthase May Reveal a Novel Sugar Signaling Pathway.
abstract: Soluble sugars not only serve as nutrients, but also act as signals for plant growth and development, but how sugar signals are perceived and translated into physiological responses in plants remains unclear. We manipulated sugar levels in transgenic plants by overexpressing sucrose synthase (SuSy), which is a key enzyme believed to have reversible sucrose synthesis and sucrose degradation functions. The ectopically expressed SuSy protein exhibited sucrose-degrading activity, which may change the flux of sucrose demand from photosynthetic to non-photosynthetic cells, and trigger an unknown sucrose signaling pathway that lead to increased sucrose content in the transgenic plants. An experiment on the transition from heterotrophic to autotrophic growth demonstrated the existence of a novel sucrose signaling pathway, which stimulated photosynthesis, and enhanced photosynthetic synthesis of sucrose, which was the direct cause or the sucrose increase. In addition, a light/dark time treatment experiment, using different day length ranges for photosynthesis/respiration showed the carbohydrate pattern within a 24-h day and consolidated the role of sucrose signaling pathway as a way to maintain sucrose demand, and indicated the relationships between increased sucrose and upregulation of genes controlling development of the shoot apical meristem (SAM). As a result, transgenic plants featured a higher biomass and a shorter time required to switch to reproduction compared to those of control plants, indicating altered phylotaxis and more rapid advancement of developmental stages in the transgenic plants.
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National University Gwangju, South Korea.
authors.forename: Quynh Anh
authors.initials: QA
authors.lastname: Nguyen
authors.affiliation: Department of Plant and Microbial Biology, University of California Berkeley Berkeley, CA, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Luan
authors.affiliation: Bio-Energy Research Center, Chonnam National University Gwangju, South Korea.
authors.forename: Seung G
authors.initials: SG
authors.lastname: Wi
authors.affiliation: School of Biotechnology, Yeungnam University Gyeongsan, South Korea.
authors.forename: Hanhong
authors.initials: H
authors.lastname: Bae
authors.affiliation: Bio-Energy Research Center, Chonnam National University Gwangju, South Korea.
authors.forename: Dae-Seok
authors.initials: DS
authors.lastname: Lee
authors.affiliation: Department of Bioenergy Science and Technology, Chonnam National UniversityGwangju, South Korea; Bio-Energy Research Center, Chonnam National UniversityGwangju, South Korea.
authors.forename: Hyeun-Jong
authors.initials: HJ
authors.lastname: Bae
keywords: CycD cyclin; WUSCHELL; endogenous sucrose; enhanced photosynthesis; shoot apical meristems; sucrose signaling pathway; sucrose synthase; sucrose-degrading SuSy activity