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 Our research focuses on the molecular mechanisms of plant how to percept, transmit, and response to environment. Through the elucidation of signal transduction in plant gravitropism and understanding the physiological effects caused by microgravity stimulus, we can identify the key genes involved in regulation of plant growth and explore their application in plant genetic engineering to improve the crop yield and quality.
Principal Investigator: Dr. Wei-Ming Cai, Professor. Email: wmcai@sippe.ac.cn
Staff: Jian-Ying Fang, Technician; Hai-Ying Chen, Research Intern; Jing Jin, Research Intern; Xian-Ying Dou, Research Intern
Graduate Students: Ai-Ping Zang; Jian-Li Duan; Li-Hua Zhao; Lu Ying
Graduated Student: Li-Wei Hu, 2005 (PhD)
 Auxin-regulated OsRGP1 and OsSuS are Involved in Gravitropic Bending of Rice Shoot Bases
Gravitropic bending of horizontally-oriented rice shoots results from the differential elongation of cells in the upper and lower halves of the shoot bases. In this study, genes encoding a reversibly glycosylated polypeptide (OsRGP1) and a sucrose synthase (OsSuS) related to sugar metabolism were identified by suppressive subtractive hybridization (SSH) as being differentially expressed in gravibending lower and upper halves of rice shoot bases. RT-PCR was used to monitor OsRGP1 and OsSuS gene expression. The two genes were differentially induced in lower and upper halves of the shoot bases during gravitropism and their expression was regulated by auxin. Gene promoter sequence analysis was consistent with these results. Treatment with the auxin transport inhibitor TIBA inhibited the asymmetric expression of OsRGP1 and OsSuS. In addition, an increase in hexose sugars was detected in the lower half of the shoot bases during gravitropism. Our data suggest that asymmetric redistribution of auxin following gravistimulation results in differentially localized OsRGP1 and OsSuS expression. Asymmetric expression of OsSuS could potentially result in a disproportionate distribution of hexose. In addition, it is possible that asymmetric expression of OsRGP1 induces cell wall polysaccharide synthesis in the lower half of shoot bases. Therefore hexose and cell wall polysaccharide accumulation in the lower half of rice shoot bases might contribute to cell expansion and subsequent gravitropic bending.
Research of PgTIP11 Transgenic Plants
The suppression subtractive hybridization technique was used to identify differentially expressed genes between hormone-autotrophic and hormone-dependent Panax ginseng callus lines. A tonoplast intrinsic protein cDNA (PgTIP1) was found to be highly and specifically expressed in hormone-autotrophic ginseng cells. When overexpressed in Arabidopsis thaliana, PgTIP1 substantially altered the plant’s vegetative and reproductive growth and development. Arabidopsis plants overexpressing PgTIP1 showed significantly enhanced seed size and seed mass plus greatly increased growth rate compared with those of the wild type. Moreover, the seeds from PgTIP1 over-expressing Arabidopsis had 1.85-fold higher fatty acid content than the wild-type control. We try to obtain PgTIP1 transgenic crops. The different expression of genes between the wild type and PgTIP1 over-expressing plants will be analyzed. We will clone the genes expressing differently in PgTIP1 over-expressing plants and study their functions related with seed growth and fatty acid metabolism.
Major Publications:
Li GW, Zhang MH, Cai WM, Sun WN, and Su WA. (2008) Characterization of OsPIP2;7, a water channel protein in rice. Plant Cell Physiology 49: 1851-1858. Li GW, Peng YH, Yu X, Cai WM, Sun WN, and Su WA. (2008) Functional and expression analysis of tonoplast intrinsic proteins in rice. Journal of Plant Physiology 165: 1879-1888. Khalid A. Khalid, Hu WL, and Cai WM. (2008) The Effects of Harvesting and Different Drying Methods on the Essential Oil Composition of Lemon Balm (Melissa officinalis L.). Jeobp 11: 342-349.
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