Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Analysis Of Gene Expression Associated With Chloroplast Development And Cold Acclimation In A Collection Of Albina And Xantha Mutants Of Barley

Jan Svenson¹ , Cristina Crosatti² , Chiara Campoli² , Roberto Bassi³ , Stefano Caffarri³ , Timothy Close¹ , Luigi Cattivelli²

¹  Department of Botany and Plant Sciences University of California, Riverside, CA, 92521-0124-USA.

²  CRA-Experimental Institute for Cereal Research Via S. Protaso 302-29017 Fiorenzuola d’Arda (PC) Italy.

³  Université Aix-Marseille II, Laboratoire de Génétique et Biophysique des Plantes Département de Biologie 163, Avenue de Luminy- 13288 Marseille Cedex 09, France.

We investigated the transcriptome of four albina and xantha barley mutants representing successive steps in chloroplast biogenesis and the corresponding wild type (WT) with the Affymetrix Barley 1 GeneChip to assess the variation of gene expression associated with chloroplast development. Moving from alb-e16 (the most extreme mutant) to xan-b12 (the genotype closest to WT) the number of genes more than 2 fold up- or down-regulated in the leaves declined from 2,391 to 896 comparing mutants against WT (19.1% to 9.0% of the transcriptome) suggesting the progressive normalization of the transcriptome as chloroplast development proceed. The up and down regulated genes were converted to the arabidopsis homologous sequences for analysis with MAPMAN software to investigate the metabolic changes controlled by chloroplast. Previously , we have shown that barley plants carrying mutations preventing chloroplast development are completely frost susceptible as well as impaired in the expression of several cold regulated genes. When the mutant transcriptome was investigated at low temperature about 70% of genes up- or down-regulated by cold in WT were not cold regulated in any chloroplast mutants and were independent to the CBF regulatory pathway. This means that the lack of cold regulation in the mutants must be due to either the presence of signaling pathway(s) normally cold-activated in WT but active at 20°C in the mutants, or the disruption of low-temperature signaling pathway(s) due to the absence of active chloroplasts. We also found evidences that photooxidative stress signaling pathway is constitutively active in the mutants.