ABSTRACT
*The delay in autumnal senescence that has occurred in recent decades has been linked to rising temperatures. Here, we suggest that increasing atmospheric CO2 may partly account for delayed autumnal senescence and for the first time, through transcriptome analysis, identify gene expression changes associated with this delay. *Using a plantation of Populus x euramericana grown in elevated [CO2] (e[CO2]) with free-air CO2 enrichment (FACE) technology, we investigated the molecular and biochemical basis of this response. A Populus cDNA microarray was used to identify genes representing multiple biochemical pathways influenced by e[CO2] during senescence. Gene expression changes were confirmed through real-time quantitative PCR, and leaf biochemical assays. *Pathways for secondary metabolism and glycolysis were significantly up-regulated by e[CO2] during senescence, in particular, those related to anthocyanin biosynthesis. Expressed sequence tags (ESTs) representing the two most significantly up-regulated transcripts in e[CO2], LDOX (leucoanthocyanidin dioxgenase) and DFR (dihydroflavonol reductase), gave (e[CO2]/ambient CO(2) (a[CO2])) expression ratios of 39.6 and 19.3, respectively. *We showed that in e[CO2] there was increased autumnal leaf sugar accumulation and up-regulation of genes determining anthocyanin biosynthesis which, we propose, prolongs leaf longevity during natural autumnal senescence.
Subject(s)
Anthocyanins/biosynthesis , Carbon Monoxide/pharmacology , Gene Expression Profiling , Gene Expression Regulation, Plant/drug effects , Populus/genetics , Seasons , Carbohydrates/analysis , Chlorophyll/metabolism , Genes, Plant/genetics , Metabolic Networks and Pathways/drug effects , Metabolic Networks and Pathways/genetics , Oligonucleotide Array Sequence Analysis , Plant Leaves/drug effects , Plant Leaves/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Reproducibility of Results , Reverse Transcriptase Polymerase Chain Reaction , Time FactorsABSTRACT
Limited information is available on the genetic variation and control for plant growth response to elevated CO(2) (e[CO(2)]). Such information is necessary to understand plant adaptation and evolution in future rising CO(2). Here, quantitative trait loci (QTL) for leaf growth, development, quality and leaf senescence were determined in a tree pedigree - an F(2) hybrid of Populus trichocarpa T. & G and Populus deltoides Marsh, following season-long exposure to either current day ambient carbon dioxide (a[CO(2)]) or e[CO(2)] at 600 microL L(-1). Leaf growth and development differed between the grandparents such that P. trichocarpa showed greater response to e[CO(2)]. In the F(2) generation, leaf development and quality traits including leaf area, leaf shape, epidermal cell area, and stomatal number, specific leaf area (SLA), and the phenology trait, canopy senescence index, were sensitive to e[CO(2)]. Sixty-nine QTL were mapped for the 19 traits of plants in a[CO(2)] while 60 QTL were mapped for plants in e[CO(2)]. The results suggest that although many QTL mapped to common positions in a[CO(2)] and e[CO(2)], confirming their importance in determining growth, there was also differential genetic control for a number of traits including leaf senescence. Candidate genes were shown to collocate to regions where response QTL mapped. This study is the first to identify candidate genes that may be important in determining plant adaptation to future high-CO(2) world.
