Abstract
Light quality response is a vital environmental cue regulating plant development. Conifers, like angiosperms, respond to the changes in light quality including the level of red (R) and far-red (FR) light, which follows a latitudinal cline. R and FR wavelengths form a significant component of the entire plant life cycle, including the initial developmental stages such as seed germination, cotyledon expansion and hypocotyl elongation. With an aim to identify differentially expressed candidate genes, which would provide a clue regarding genes involved in the local adaptive response in Scots pine (Pinus sylvestris) with reference to red/far-red light; we performed a global expression analysis of Scots pine hypocotyls grown under two light treatments, continuous R (cR) and continuous FR (cFR) light; using Pinus taeda cDNA microarrays on bulked hypocotyl tissues from different individuals, which represented different genotypes. This experiment was performed with the seeds collected from northern part of Sweden (Ylinen, 68?N). Interestingly, gene expression pattern with reference to cryptochrome1, a blue light photoreceptor, was relatively high under cFR as compared to cR light treatment. Additionally, the microarray data analysis also revealed expression of 405 genes which was enhanced under cR light treatment; while the expression of 239 genes was enhanced under the cFR light treatment. Differentially expressed genes were re-annotated using Blast2GO tool. These results indicated that cR light acts as promoting factor whereas cFR antagonises the effect in most of the processes like C/N metabolism, photosynthesis and cell wall metabolism which is in accordance with former findings in Arabidopsis. We propose cryptochrome1 as a strong candidate gene to study the adaptive cline response under R and FR light in Scots pine as it shows a differential expression under the two light conditions.
Highlights
Plants as sessile organisms, rely on their adaptive plasticity to respond to the changes in their local environmental conditions, to optimise growth and reproduction [1,2]
With an aim to identify differentially expressed candidate genes, which would provide a clue regarding genes involved in the local adaptive response in Scots pine (Pinus sylvestris) with reference to red/far-red light; we performed a global expression analysis of Scots pine hypocotyls grown under two light treatments, continuous R and continuous FR light; using Pinus taeda cDNA microarrays on bulked hypocotyl tissues from different individuals, which represented different genotypes
The focus of our study was to identify candidate genes for studying adaptive cline in Scots pine, based on differential gene expression pattern in Scots pine seedlings grown under continuous R (cR) and continuous FR (cFR) light treatments; throughout the result and discussion chapter we have referred to the changes in gene expression under cR with reference to the expression pattern under cFR light and vice versa
Summary
Rely on their adaptive plasticity to respond to the changes in their local environmental conditions, to optimise growth and reproduction [1,2]. Light as a main environmental regulator, plays a central role in photosynthesis, photoperiodism, phototropism and photomorphogensis. Photomorphogenesis is mediated by the perception of the light conditions by at least four families of photoreceptors: cryptochromes and phototropins, which monitor the blue and ultraviolet regions of the spectrum; the phytochromes, which mainly monitor the red (R) and far-red (FR) regions of the solar spectrum; and the ultraviolet B photoreceptor [3,6,7]. The phytochrome (phy) family consists of five members phyA through phyE in Arabidopsis [8]. Phytochromes exist as two interconvertible isoforms: a R-absorbing Pr form and a FR-absorbing Pfr form, of which Pfr is the physiologically active state [8]. On absorption of R light, Pr is converted to the Pfr form; and Pfr absorbs FR light, and gets converted to the Pr form. Two cryptochromes (cry) have been characterised in Arabidopsis—cry and cry encoded by CRY1 and CRY2 genes respectively [10]
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