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Abstract Detail


Cell Walls

Shin, Sung-Bong [1], Palusa, Saiprasad [2], Golovkin, Maxim [3], Richardson, Dale [2], Reddy, Anireddy S. N. [2].

Regulation of expression of putative pectate lyase genes and analysis of pectate lyase activity in different tissues in Arabidopsis.

Pectins, major components of primary cell walls of all land plants, are important for maintaining the structural integrity and strength of the cell wall in higher plants. Pectins are a family of complex polysaccharides with 1,4-linked α-D-galactosyluronic acid residues. These include homogalacturonan, rhamnogalacturonan-I and rhamnogalacturonan-II. Some studies indicate that enzymes involved in pectin biosynthesis, modification and degradation have important roles in growth and developmental processes and in plant defense. Pectate lyases (PLs) or pectate transeliminases, a family of endo-acting depolymerizing enzymes, cleave α-1,4-glycosidic linkages in homogalacturonan of pectate. Although PLs from plant pathogenic bacteria have been extensively characterized, relatively little is know about plant pectate lyases and their regulation. To further our understanding of pectate lyases in photosynthetic organisms, we first analyzed the completely sequenced genomes of Arabidopsis, rice and poplar, a green alga (Chlamydomonas reinhardtii), a red alga (Cyanidioschyzon merolae) and a diatom (Thallasiosira pseudonana) for genes encoding pectate lyase-like (PLL) proteins. In the genomes of three basal photosynthetic eukaryotes (C. reinhardtii, C.merolae and T. pseudonana) no PLL sequences were found whereas 26, 22 and 14 PLLs were idenfied in Arabidopsis, poplar and rice, respectively. We then used a semi-quantitative approach to perform comprehensive expression analysis of all 26 Arabidopsis PLL genes in different organs, pollen and seedlings of different ages using reverse transcription PCR (RT-PCR). The expression of PLLs varied considerably in different organs with no expression of some PLLs in vegetative organs. Interestingly, all PLL genes are expressed in flowers. Several PLLs are expressed highly in pollen, suggesting a role for these in pollen development and/or function. Analysis of expression of all PLL genes in seedlings treated with hormones, abiotic stresses and elicitors of defense responses revealed significant changes in the expression of some PLLs without affecting the other PLLs. The stability of transcripts of PLLs varied considerably among different genes. Together our results indicate a complex regulation of expression of PLLs and involvement of PLLs in some of the hormonal and stress responses. Since PL activity was not demonstrated in Arabidopsis, we are currently quantifying PL enzyme activity in various Arabidopsis tissues using different substrates. Results of these analyses will also be presented at the meeting.


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1 - Colorado State University, Biology, 1878 campus delivery, Fort Collins, CO, 80523, USA
2 - Colorado State University, Biology
3 - Thomas Jefferson University, Biotechnology Foundation Laboratories

Keywords:
Pectate Lyase
Pectin
Arabidopsis.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P17024
Abstract ID:1095


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