Differential tissue/organ-dependent expression of two sucrose- and cold-responsive genes for UDP-glucose pyrophosphorylase in Populus.
Plant UDP-glucose (UDPG) pyrophosphorylase (UGPase) is involved in the production/metabolism of UDPG, a key metabolite for sucrose and cell wall biosynthesis. Two highly similar cDNAs (UGP1 and UGP2) corresponding to UGPase were isolated from cDNA libraries of hybrid aspen (Populus tremula x tremuloides). Expression of both UGPs, as studied by DNA microarrays and EST abundance, was compared to that of three sucrose synthase genes (SUS1-3), also involved in UDPG synthesis. Generally, the UGPs had lower expression than SUS1 and SUS2 genes (especially in tension wood and cambium), with the notable exception of leaves, primary roots and flowers. Based on real-time quantitative PCR, UGP1 in root xylem, leaves and male flowers was by far the predominant transcript, while in other tissues both UGP1 and UGP2 had comparable expression. In leaves, the UGP1 gene, but not UGP2, was upregulated by light and short-term sucrose feeding. Cold treatment led to dramatic organ-specific changes in relative expression of both genes, with UGP2 being upregulated either transiently (leaves), long-term (stems) or not at all (roots), whereas UGP1 was cold-upregulated in all organs. Individual or overall UGP expression patterns only weakly correlated with UGPase activity/protein; however, UGPase activity and protein were correlated in all tissues/conditions. The data suggest that UGPs are differentially expressed at the tissue level and in response to metabolic feedback (sucrose) and cold stress, and point to a tight posttranscriptional/translational control and, possibly, distinct roles for those genes.
Meng
Meng
M
Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, 901 87 Umeå, Sweden.
Geisler
Matt
M
Johansson
Henrik
H
Mellerowicz
Ewa J
EJ
Karpinski
Stanislaw
S
Kleczkowski
Leszek A
LA
D003080:Cold Temperature; D018076:DNA, Complementary; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism*; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase / Q000235:genetics* / Q000378:metabolism; D052584:Xylem / Q000235:genetics / Q000378:metabolism
D018076:DNA, Complementary; D010940:Plant Proteins; D013395:Sucrose; D005964:Glucosyltransferases; C022699:sucrose synthase; C102599:sucrose synthase kinase; D017346:Protein Serine-Threonine Kinases; D005957:UTP-Glucose-1-Phosphate Uridylyltransferase