Poster: Mineral nutrition
Abs #
206: A survey of the vascular transcriptome in Citrus sinensis L. Osbeck and its applications for expression analysis during nitrogen stress
To accelerate the molecular analysis of citrus vascular tissue, an investigation of the phloem transcriptome using expressed sequence tags (ESTs) was undertaken. Total RNA was extracted from healthy greenhouse-grown Citrus sinensis L. Osbeck phloem tissue and was used to construct a cDNA library that generated 2623 high quality ESTs. Putative transcripts were annotated using the Gene Ontology classification system and categorized according to biological and molecular function. Function identity was assigned to 1405 of these sequences. Genes involved with plant stress such as metallothionein-like proteins, miraculin-like proteins, chitinase and type I proteinase inhibitor were highly abundant. Photosynthetic proteins such as chlorophyll A/B binding protein, Rubisco and plastocyanin were absent from this EST set. The remaining 1218 ESTs failed to significantly match known sequences in the public databases and are expected to represent genes specific to perennials and perhaps citrus. Membrane-based arrays were constructed using the complete set of high quality EST cDNA clones. Vascular tissue RNA from citrus grown under high soil nitrogen levels (200 ppm complete nitrate solution) and plants that received foliar application of 0.2% urea was used to generate probes for array analysis. Expression confirmation was accomplished using quantitative RT-PCR. Gene expression by metabolic pathways and class will be discussed in light of nitrogen stress and route of absorption of nitrogen source.
