Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2010
Publication Date: 6/15/2010
Citation: Bilgin, D.D., Zavala, J.A., Zhu, J., Clough, S.J., Ort, D.R., Delucia, E.H. 2010. Biotic Stress Globally Down-Regulates Photosynthesis Genes. Plant Cell and Environment. doi: 10.1111/j.1365-3040.2010.02167.x. Interpretive Summary: Photosynthesis is a complex process that plants use to generate energy from sunlight. Many genes related to photosynthesis seem to be rapidly turned down in their expression levels when plants are assaulted by pathogens and insects. To investigate whether this is a universal phenomenon, we surveyed the literature for studies that looked at photosynthetic gene expression in response to a wide variety of pathogen and insect attacks. We cross compared this gene expression data and identified common patterns of gene expression across multiple studies involving different plants such as Arabidopsis, poplar, soybean, and tobacco. This manuscript details our finding of the universal nature of this down regulation of genes related to photosynthesis in response to biotic assaults. The information will be of interest to plant biologist, especially those that focus on pathology and herbivory.
Technical Abstract: Upon herbivore and pathogen attacks, plants switch from processes supporting growth and reproduction to defense by inducing a set of defense genes and down-regulating most of the nuclear encoded photosynthetic genes. To determine if this transcriptional response is universal we used transcriptome data generated from microarray experiments after twenty-two different forms of biotic damage, including viral, fungal, bacterial and herbivore attack on eight different plant species. Mechanical wounding, phytohormone and regurgitant treatments also were included in the analysis. The hierarchical cluster analysis of photosynthesis light reaction and pigment synthesis genes revealed that transcript levels decreased uniformly regardless of the type of attack. Similarly, transcripts for genes coding for proteins unique to the Calvin cycle were uniformly down-regulated following biotic damage. The corresponding up-regulation of genes coding for the synthesis of Jasmonic acid and those involved in the responses to salicylic acid and ethylene, core defense hormones, suggest that the down-regulation of photosynthesis was related to mounting a defense. The determination of subcellular localization of co-expressed gene clusters showed that the transcript levels of 84% of the genes that carry a chloroplast targeting peptide sequence decreased. The majority of these down-regulated, chloroplast-targeted genes shared common regulatory elements, such as G-box (CACGTG), T-box (ACTTTG) and SORLIP (GCCAC) motifs. Strong convergence in the response of transcriptions suggests that the universal down-regulation of photosynthesis is an adaptive response to biotic attack, but the benefits of this response are not yet known.