Abstract
The outermost layer epidermis of a plant stem plays an important role in protection and environment-sensing. The mechanisms of sensing and response to the environment through the stem epidermis remain unclear. Here we report enriched expression of genes involved in stress resistance and signal transduction functions in the stem epidermis of both D. purpureus and A. thaliana by cDNA cloning and QPCR in D. purpureus and by analysis using dataset from a genome-wide comparison with cDNAs differentially expressed between the epidermis and inner parts of top and base stem in A. thaliana. Among 188 cDNAs from the stem epidermis of D. purpureus, 13% and 17% were related to signal transduction and defense respectively. Most of them were up-regulated more in the stem epidermis than the inner stem, as well as in A. thaliana. Also, the distribution of the numbers and specificities of up-regulated genes related to signal transduction and regulatory networks in the epidermis and inner stem revealed the possibility of positional differences in regulation. The results revealed the importance of the epidermis in signal transduction and plant defence.
Highlights
The epidermis is a protective layer covering the entire plant, usually comprising one to a few layers of cells: the outmost cuticle layer and the epidermis layer composed of basic cells, trichomes and guard cells
We analyzed the functional pattern of genes expressed in stem epiderm of D. purpureus L., further confirmed by QPCR on some representative genes, and compared with the similar genes from A. thaliana
The differential gene expression profiles in epidermis and inner part of stem from both D. purpureus L. and A. thaliana reaveal that defense and signal transduction is important function in stem epidermis. 13% and 17% of genes from 188 sequenced cDNAs expressed in stem epidermis of D. purpureus L. are belong to signal transduction and defense pathways respectively
Summary
The epidermis is a protective layer covering the entire plant, usually comprising one to a few layers of cells: the outmost cuticle layer and the epidermis layer composed of basic cells, trichomes and guard cells. The epidermis begins to differentiate as early as the 8-cell stage, and differentiation of epidermal cell types appears later in embryo development [1,2,3]. In growing seedlings and mature plants, the epidermal cells of a fully developed plant continue to divide and differentiate into specific cell types at specific sites within the epidermis [4], and secrete cutin and wax to cover the surface, forming a protective layer [5,6]. The expression profile of genes in the epidermis changes with developmental stage [11,12,13] and cell type [7,12,13]
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