Seasonal activity of uridine 5'-diphosphoglucose:coniferyl alcohol glucosyltransferase in relation to cambial growth and dormancy in conifers

Abstract

Uridine 5'-diphosphoglucose:coniferyl alcohol glucosyltransferase (CAGT), the enzyme catalyzing synthesis of coniferin from coniferyl alcohol and uridine 5'-diphosphoglucose, was investigated throughout an annual cycle of cambial growth and dormancy in Pinus banksiana Lamb. During dormancy, CAGT activity was not detected in the cambium. CAGT became weakly active in springtime when fusiform cells of the lateral meristem changed from densely protoplasmic to highly vacuolated states, just prior to resumption of cell-division activity. During cambial growth and xylogenesis, CAGT activity in cambial derivatives was greater than that found in the cambial zone. In both cambial zone and developing xylem, seasonally changing CAGT activity paralleled seasonal variation in endogenous coniferin content. CAGT activity disappeared when the cambium entered dormancy in August, prior to completion of lignification in the last differentiating latewood tracheids. In vitro, exogenous coniferin at 0.1 mmol ·L-1 promoted CAGT activity (optimum pH 7.8, temperature 40°C); however, coniferin at >10 mmol ·L-1 inhibited CAGT activity, in agreement with endogenous coniferin content of developing xylem not exceeding that level. The results indicate that the promoter controlling CAGT gene expression may be cambial specific and linked to the overall control of seasonal cambial growth and dormancy.Key words: cambium, coniferin, lignin, phenology, Pinus banksiana, xylogenesis.

Gene Expression during Formation of Earlywood and Latewood in Loblolly Pine: Expression Profiles of 350 Genes

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Lignan accumulation in two-phase cultures of Taxus x media hairy roots

“…2001). Moreover, the activity of UDPG: coniferyl alcohol glucosylotransferase, an enzyme that catalyses the transfer of glucose from UDPG to coniferyl alcohol in cambium and developing xylem, is closely coupled with cambium activity (Savidge and Förster 1998).…”

Yukon Taiga – Past, Present and Future

“…In addition, little if any photosynthesis occurs throughout long dark taiga winters, and for tree survival it is therefore essential that sufficient storage reserves are present by the end of each summer's growing season (Lloyd et al, 2002;Röser et al, 2002;Zarter et al, 2006). Following their long winter, subarctic conifers are further drained of vital stored chemical energy due to their intrinsic tendency to commence root and cambium growth in late spring before buds have broken and new needles matured (Savidge & Förster, 1998). Standing dead trees (i.e., snags) are common in taiga and, in the absence of disease or obvious physical damage, it appears that the taiga-tundra treeline manifests that point where loss of metabolic reserves exceeds a tree's ability to support its respiratory needs.…”