Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

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La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d’Eucalyptus globulus Labill

International audienc

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch

Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A.Peer reviewe

Genome sequencing and population genomic analyses provide insights into the adaptive landscape of silver birch.

Silver birch (Betula pendula) is a pioneer boreal tree that can be induced to flower within 1 year. Its rapid life cycle, small (440-Mb) genome, and advanced germplasm resources make birch an attractive model for forest biotechnology. We assembled and chromosomally anchored the nuclear genome of an inbred B. pendula individual. Gene duplicates from the paleohexaploid event were enriched for transcriptional regulation, whereas tandem duplicates were overrepresented by environmental responses. Population resequencing of 80 individuals showed effective population size crashes at major points of climatic upheaval. Selective sweeps were enriched among polyploid duplicates encoding key developmental and physiological triggering functions, suggesting that local adaptation has tuned the timing of and cross-talk between fundamental plant processes. Variation around the tightly-linked light response genes PHYC and FRS10 correlated with latitude and longitude and temperature, and with precipitation for PHYC. Similar associations characterized the growth-promoting cytokinin response regulator ARR1, and the wood development genes KAK and MED5A

Dehydrins in Scots pine tissues:responses to annual rhythm, low temperature and nitrogen

Abstract Natural seasonal variation and the effects of cold treatment and nitrogen fertilization on protein expression with special emphasis on dehydrin proteins, were studied using different aged Scots pine (Pinus sylvestris L.). Several different dehydrins were found and their expression depended on the tissue type, tree age or specific treatment. Their concentrations fluctuated seasonally and in response to nitrogen fertilization, but no effects of low temperature on the dehydrins of seedlings were observed. A 60-kDa dehydrin was associated with cold acclimation in the bud and bark tissues of mature trees and in the needles of seedlings. In the needles of mature trees, this dehydrin was associated with springtime desiccation, which was detected as a significant decrease in the osmotic potential of needles. The quantity and quality of soluble proteins altered seasonally in Scots pine tissues, but low temperature treatment alone did not have any effect on the proteins. Soluble protein concentration increased during autumn and decreased in spring in buds and bark, but not in the needles of mature trees. In needles of seedlings, however, protein concentrations altered seasonally. Several proteins, of varying molecular weights, were more abundant in winter in all the tissues studied and some increased in concentration in the nitrogen-fertilized seedlings. The role of these proteins as a storage reserve in Scots pine is discussed. The osmotic potential of needles showed seasonal fluctuation, being high in the summer and low during the winter. Low temperature treatment decreased the osmotic and water potential of needles and increased the concentrations of soluble sugars in seedlings. Based on carbohydrate analyses, the metabolism of seedlings acclimated to low temperature in less than ten days. Nitrogen fertilization increased the content of total nitrogen and the soluble protein concentrations in the needles of seedlings and the growth both in the mature trees and seedlings. Although the frost resistance showed no response to nitrogen-fertilization, the soluble proteins and dehydrins were affected in a manner that suggested an earlier growth resumption of spring in the fertilized trees