Abstract
Jatropha curcas L. (Family – Euphorbiaceae) is a perennial tree of special interest due to its potential as a biofuel plant with high carbon sequestration. In this study, physiological investigations coupled with transcriptomics in relation to photosynthesis were evaluated in Jatropha grown under ambient (395 ppm) and elevated (550 ppm) CO2 atmosphere. Morphophysiological analysis revealed that Jatropha sustained enhanced photosynthesis during its growth under elevated CO2 for one year which might be linked to improved CO2 assimilation physiology and enhanced sink activity. We sequenced and analyzed the leaf transcriptome of Jatropha after one year of growth in both conditions using Illumina HiSeq platform. After optimized assembly, a total of 69,581 unigenes were generated. The differential gene expression (DGE) analysis revealed 3013 transcripts differentially regulated in elevated CO2 conditions. The photosynthesis regulatory genes were analysed for temporal expression patterns at four different growth phases which highlighted probable events contributing to enhanced growth and photosynthetic capacity including increased reducing power, starch synthesis and sucrose mobilization under elevated CO2. Overall, our data on physiological and transcriptomic analyses suggest an optimal resource allocation to the available and developing sink organs thereby sustaining improved photosynthetic rates during long-term growth of Jatropha under CO2 enriched environment.
Highlights
Atmospheric carbon dioxide concentration [CO2] has increased from 280 μmol mol−1 to current 395 μmol mol−1 since the pre-industrial era and is expected to reach between 500–900 μmol mol−1 by the end of this century[1]
Morphophysiological and biochemical variations were monitored during growth of Jatropha under ambient and elevated CO2 conditions at regular intervals for both seasons
The light-saturated photosynthetic rate (Asat) and apparent quantum efficiency (AQE; calculated as an initial slope of A/Q curve) were recorded to be significantly higher (~28 μmol m−2 s−1; ~0.030) at all four time points under elevated CO2 in comparison to ambient CO2 grown plants (~18 μmol m−2 s−1; ~0.020) which was sustained during both seasons (P < 0.01) (Fig. 1a, Table 1)
Summary
Atmospheric carbon dioxide concentration [CO2] has increased from 280 μmol mol−1 to current 395 μmol mol−1 since the pre-industrial era and is expected to reach between 500–900 μmol mol−1 by the end of this century[1]. The rapid growth of these trees allows the analysis of their responses to elevated [CO2] over a complete production cycle[6]. Recent advancements in generation sequencing technologies like Solexa/Illumina platform based de novo RNA-sequencing and high throughput deep sequencing have allowed discovery of new genes, analysis of specific transcripts, gene expression and generation of transcript sequences of non-model organisms[14]. This approach has accelerated better understanding of complex transcriptional patterns and measurements of gene expression in different tissues or at different stages of plant development in response to varying external environments. Few transcriptome studies, reported for growth of Jatropha under different environmental conditions, were limited to seedlings or pot-grown plants with no reports on plants grown for longer durations in field conditions[19,20,21]
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