Minisymposium 3: Global Change

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Abs # M0302: Acclimation of the maize transcriptome to CO₂ enrichment

Presenter:	Prins, Anneke       Contact Presenter
Authors	Prins, Anneke  (A) (B)  Driscoll, Simon P (A)   Verrier, Paul  (C)   Kunert, Karl  (B)   Foyer, Christine H (A)
Affiliations:	(A): Crop Performance and Improvement Division, Rothamsted Research (B): FABI, Botany Department, (C): Biomathematics and Bioinformatics Division, Rothamsted Research

Much controversy surrounds the responses of C₄ plants to increasing atmospheric CO₂ availability. In the present study, the maize plants that were grown in controlled environments with CO₂ enrichment (700 μL.L CO₂ ) were significantly taller than those grown at 350μL.L CO₂ but they had the same number of leaves. High CO₂ availability led to an increase in stomatal index and a decrease in chlorophyll and protein. The abaxial surface had higher rates of photosynthesis than the adaxial surface. While photosynthesis rates on the abaxial surface was largely independent of CO₂ availability, the adaxial surface showed responses to CO₂ that were more similar to those observed in C₃ leaves. To determine whether CO₂ enrichment produced a characteristic transcriptome signature in young and senescent leaves, we undertook a series of micro-array experiments. RNA was extracted from leaf 12 (young source leaf) and leaf 3 (senescent source leaf) of 8 week-old maize plants using. RNA samples were purified, converted to cDNA and used to synthesise biotin-labelled cRNA. Labelled cRNA was hybridised to Affymetrix corn chips, which have 17,555 probe sets that interrogate approximately 14,850 transcripts that in turn represent 13,339 genes. Raw expression intensity values for replicate samples were averaged and converted to log₂ values for comparison of transcript expression level. Transcripts that showed a 50% difference in expression were selected at a significance value of p<0.005. Unknown transcripts that showed differential expression were identified by determining the homology of the probeset to other genes falling within the same cluster at UniGene (Genbank, NCBI). Unknown transcripts were also identified by homology searches comparing the probeset target sequence with known protein sequences using the blastx module. For homology searches a minimum homology of 50% was selected. Surprisingly, although about 3000 transcripts were differentially expressed in senescent leaves compared to young leaves, only18 high CO₂ -induced transcripts were common to both mature and senescent leaves