Poplar Wood Rays Are Involved in Seasonal Remodeling of Tree Physiology    

Abstract

Understanding seasonality and longevity is a major challenge in tree biology. In woody species, growth phases and dormancy follow one another consecutively. In the oldest living individuals, the annual cycle may run for more than 1,000 years. So far, however, not much is known about the processes triggering reactivation from dormancy. In this study, we focused on wood rays, which are known to play an important role in tree development. The transition phase from dormancy to flowering in early spring was compared with the phase of active growth in summer. Rays from wood samples of poplar (Populus 3 canescens) were enriched by laser microdissection, and transcripts were monitored by poplar whole-genome microarrays. The resulting seasonally varying complex expression and metabolite patterns were subjected to pathway analyses. In February, the metabolic pathways related to flower induction were high, indicating that reactivation from dormancy was already taking place at this time of the year. In July, the pathways related to active growth, like lignin biosynthesis, nitrogen assimilation, and defense, were enriched. Based on "marker" genes identified in our pathway analyses, we were able to validate periodical changes in wood samples by quantitative polymerase chain reaction. These studies, and the resulting ray database, provide new insights into the steps underlying the seasonality of poplar trees.

Laser Capture Microdissection Protocol for Xylem Tissues of Woody Plants

“…This analysis provided a cell specific lignin profile, but no RNA was isolated. The studies of Larisch et al (2012) and Zheng et al (2016) illustrate the potential of LCM method, while at the same time highlighting the need for a robust xylem-cell-specific LCM protocol which does not compromise RNA quality.…”

“…Larisch et al (2012) used LCM to separate developing and mature wood from twigs of poplar ( Populus × canescens ), and subsequently analyzed the mature wood transcriptome using whole-genome microarrays (Larisch et al, 2012). The authors argued that ray cells, as the main living cells in mature wood, contributed most to the isolated RNA.…”

Comparative proteomic analysis of Populus trichocarpa early stem from primary to secondary growth

“…Of all, each of 30 differentially accumulated protein species was identified in multiple spots, and their protein name and spot number were labeled with bold in Table 1. For example, 7 different protein spots (15,18,19,21,28,48 and 64) were found to be an identical GDSL-like lipase/acylhydrolase protein species, which indicates that posttranslational modifications or protein splice variants occurred in these proteins.…”

“…Nevertheless, trees constitute the optimal model for investigating plant secondary vascular development. Tree wood is manufactured by a succession of major steps including cell division, cell expansion, cell wall thickening (cellulose, hemicellulose and lignin biosynthesis and deposition), programmed cell death, and heartwood formation [11][12][13][14][15]. However, there is limited understanding of the molecular basis of tree wood formation thus far.…”

Tracing a key player in the regulation of plant architecture: the columnar growth habit of apple trees (Malus × domestica)

“…Additional downstream effects related to dormancy induction are the upregulation of genes associated with cold hardiness and drought, defense, carbohydrate synthesis and transport, cell wall biosynthesis or modification as well as RNA metabolism and chromatin modification/remodeling (Ruttink et al 2007;Park et al 2008;Ko et al 2011). In contrast, the transition from dormancy to active growth is characterized by the induction of flowering pathways, RNA metabolism and protein biosynthesis and transport (Larisch et al 2012). It has been found that SAM cells are symplastically isolated during the dormant period due to the formation of a callose block at the plasmodesmata (Rinne and van der Schoot 1998;Rinne et al 2001;Rinne et al 2011).…”