Xu, Fuyu , Joshi, Chandrashekhar P. .
Genome-wide expression analysis of Sucrose Synthase Genes in the Poplar Trees.
Sucrose synthases (SUS) are the key regulatory enzymes involved in the sucrose metabolism of plants that play significant roles in the process of cellulose biosynthesis. It has been proposed that SUS directly channel UDP-glucose substrate to cellulose synthesizing machinery consisting of multiple cellulose synthases. The advent of the complete genome sequence of Populus trichocarpa has now provided a unique opportunity to explore the structure, expression and evolution of the entire SUS gene family in poplars. Eleven putative SUS gene models were identified, seven of which are full-length and potentially functional, and the other four appear to be inactive pseudogenes. These seven SUS genes from poplars (PtSUS1-PtSUS7) consist of 12-15 exons with the total gene length of 3.5 to 5.5 kb. SUS transcript levels were compared from various tissues of both cottonwood (P. trichocarpa) and aspen (P. tremuloides) and the expression patterns were found to be highly similar in both these species. PtSUS1, PtSUS2 and PtSUS6 were predominantly expressed in all organs examined while the remaining four SUS were only weakly expressed in the same tissues. Poplars quickly respond to tension stress by producing cellulose–rich tension wood on the upper side and cellulose-poor opposite wood on the lower side of the bent stem. During the time course experiment of 1-21 days of tension stress, PtrSUS1 and 2 were upregulated on tension side, PtSUS3 and 4 upregulated on opposite side and, PtSUS6 and 7 were upregulated first during early stress and the transcript levels progressively plummeted later on. These complex patterns provide a new insight into the possible distinct functions of each SUS member in the poplar metabolism. Phylogenetic analyses of 77 available full-length SUS sequences from higher plants showed that they can be divided into four groups, namely Dicot-specific SUS Group, Monocot-specific SUS Group, Dicot-Monocot Common SUS Group-1, and Dicot-Monocot Common SUS Group-2. Experiments with genetic manipulation of specific SUS genes in transgenic poplars are currently in progress and it is hoped that these results may assist in genetic improvement of overall cellulose production in economically important trees via improved supply of UDP-glucose substrates.
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1 - Michigan Technological University, Biotechnological Research Center, School of Forest Resources and Environmental Sciences, 1400 Townsend Drive, Houghton, MI, 49931, USA
2 - Michigan Technological University, Biotechnological Research Center, School of Forest Resources and Environmental Sciences, 1400 Tonsend Drive, Houghton, MI, 49931, USA
Sucrose synthase genes
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM