Towards deciphering phloem: a transcriptome analysis of the phloem of Apium graveolens

• Published in: The Plant journal : for cell and molecular biology Vol. 36; no. 1; pp. 67 - 81
• Main Authors: Vilaine, F., Palauqui, J.‐C., Amselem, J., Kusiak, C., Lemoine, R., Dinant, S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.10.2003; Blackwell Science; Wiley
• Subjects: Apium - genetics; Biological and medical sciences; Blotting, Northern; cDNA macroarray; celery; Cell biochemistry; Cell physiology; Cloning, Molecular; differential gene expression; DNA, Complementary - chemistry; DNA, Complementary - genetics; EST; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Gene Library; Genes, Plant - genetics; Genes. Genome; Life Sciences; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Oligonucleotide Array Sequence Analysis - methods; phloem; Phylogeny; Plant Leaves - genetics; Plant physiology and development; Plant Structures - genetics; Sequence Analysis, DNA; Vegetal Biology; xylem; xylem; Biological model; EST; Apium graveolens; Gene expression; Structure function relationship; differential gene expression; Phloem; celery; Gene; Dicotyledones; Angiospermae; Spermatophyta; Umbelliferae; Molecular biology; Expressed sequence tag; cDNA macroarray; phloem; differentiel gene expression
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.2003.01855.x

Summary Events occurring in the phloem tissue are key to understanding a wide range of developmental and physiological processes in vascular plants. While a considerable amount of molecular information on phloem proteins has emerged in the past decade, a unified picture of the molecular mechanisms involved in phloem differentiation and function is still lacking. New models to increase our understanding of this complex tissue can be created by the development of global approaches such as genomic analysis. In order to obtain a comprehensive overview of the molecular biology of the phloem tissue, we developed a genomic approach using Apium graveolens as a model. cDNA libraries were constructed from mRNAs extracted from isolated phloem of petioles. Expression data obtained from the analysis of 989 expressed sequence tags (ESTs) and the transcript profile deduced from a cDNA macroarray of 1326 clones were combined to identify genes showing distinct expression patterns in the vascular tissues. Comparisons of expression profiles obtained from the phloem, xylem and storage parenchyma tissues uncovered tissue‐specific differential expression patterns for given sets of genes. The major classes of mRNAs predominantly found in the phloem encode proteins related to phloem structure, metal homeostasis or distribution, stress responses and degradation or turnover of proteins. Of great interest for future studies are the genes we found to be specifically expressed in the phloem but for which the function is still unknown, and also those genes described in previous reports to be up or downregulated by specific interactions. From a broader prospective, our results also clearly demonstrate that cDNA macroarray technology can be used to identify the key genes involved in various physiological and developmental processes in the phloem.