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Juvenile Coffee Leaves Acclimated to Low Light Are Unable to Cope with a Moderate Light Increase.

ABSTRACT: The understorey origin of coffee trees and the strong plasticity of Coffea arabica leaves in relation to contrasting light environments have been largely shown. The adaptability of coffee leaves to changes in light was tested under controlled conditions by increasing the illumination rate on C. arabica var. Naryelis seedlings acclimated to low light conditions and observing leaf responses at three different developmental stages (juvenile, growing and mature). Only mature leaves proved capable of adapting to new light conditions. In these leaves, different major mechanisms were found to contribute to maintaining a good photosynthetic level. With increased illumination, a high photosynthetic response was conserved thanks to fast nitrogen remobilization, as indicated by SPAD values and the photorespiration rate. Efficient photoprotection was accompanied by a great ability to export sucrose, which prevented excessive inhibition of the Calvin cycle by hexose accumulation. In contrast, in younger leaves, increased illumination caused photodamage, observable even after 9 days of treatment. One major finding was that young coffee leaves rely on the accumulation of chlorogenic acids, powerful antioxidant phenolic compounds, to deal with the accumulation of reactive oxygen species rather than on antioxidant enzymes. Due to a lack of efficient photoprotection, a poor ability to export sucrose and inadequate antioxidant protection, younger leaves seemed to be unable to cope with increased illumination. In these leaves, an absence of induced antioxidant enzyme activity was accompanied, in growing leaves, by an absence of antioxidant synthesis or, in juvenile leaves, inefficient synthesis of flavonoids because located in some epidermis cells. These observations showed that coffee leaves, at the beginning of their development, are not equipped to withstand quick switches to higher light levels. Our results confirm that coffee trees, even selected for full sunlight conditions, remain shade plants possessing leaves able to adapt to higher light levels only when mature.

SUBMITTER: Campa C

PROVIDER: S-EPMC5509796 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose: Acclimation referes to reversible responses that plants trigger under frequently and moderate changes in natural environments, mostly light intensity and temperature. To better understand acclimation in Arabidopsis thaliana, modulators and integrators for this process should be identified. To achieve this goal, a dynamic set-up was designed to systematically cultivate Arabidopsis plants under moderate high light, heat and cold and a multiple high-throughput strategy was conducted to monitor changes in transcriptome, proteome and metabolome. As part of this comprehensive characterisation, lncRNA-Seq has been carried out to investigate transcriptome changes and further integrated in conditional correlation networks. Methods: lncRNA-Seq libraries were prepared from 14-d-old plants cultivated under standard control conditions or acclimated to high light, cold or heat for 4 d and then de-acclimated under normal conditions for 4 additional days. Standard Illumina protocols were used for lncRNA-Seq sequencing. Unless some quality issue in libraries was detected, triplicates for 3 independent plants were used. Adaptor sequences were removed with Trimmomatic and resulting reads mapped to the Arabidopsis genome (Araport11) with Tophat 2.1.1. FPKM reads were quantified with Cufflinks to provide processed data files and differential expression analysis were conducted with featureCounts/DEseq2 pipeline. Results: lncRNA-Seq libraries contained 10 milion reads each. Transcript analysis for differential gene expression was conducted according to the Tophat/featureCounts/DESeq2 pipeline. To declare significant differences, a cut-off for absolute log2(FC) ≥ 1 compared to the corresponding control and FDR ≤ 0.05 was applied. Transcripts significantly different in at least one time-point were considered for subsequent analysis. Accordingly, high light treatments caused changes in 2683 transcripts, followed by 3470 under heat and 6882 under cold. Further data analysis revealed that more than 12% of all altered transcripts were commonly miss-regulated among the three treatments. From a dynamic point of view, transcriptional changes occurred from 3h to 4d of treatment in all treatments and tend to recover to the initial state after 2 and 4d of de-acclimation. Conclusions: the reversibility of the transcriptional changes during the recovery phase validated the conditions of our set-up to investigate acclimation. Moreover, the existance of a common fraction of transcripts that responded to the three conditions unveiled a central response to acclimation.

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Juvenile Coffee Leaves Acclimated to Low Light Are Unable to Cope with a Moderate Light Increase.

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