SAR genes

Salicylic acid is an inducer of antifungal proteins (Figure 4.38) and is proposed to activate the expression of SAR genes in the plant.21... 

Fig. 1. SAR cDNA families in tobacco. The relationships and functions of the different gene families from tobacco are described. The asterisk below each class denotes that the cDNA has been expressed in transgenic tobacco. The class I chitinase and class I glucanase are not SAR genes as defined in the text.

The final SAR gene family, SAR8.2, comprises several highly related cDNAs which were isolated by differential screening of a tobacco cDNA library constructed from RNA of induced resistant leaves (D. Alexander et al., unpublished data). The cDNA encodes a basically-charged protein of about 50 residues, which has not been isolated and whose function is unknown. 

While it seems clear that the cell types that respond to SA using the PR-la promoter are the mesophyll cells of the leaf, it may be premature to generalise this response to all of the SAR genes. However, it is interesting that the observed expression pattern is consistent with the observation that SAR protects best against foliar pathogens. 

SAR genes are induced to high levels and expressed for many days. Large amounts of proteins are synthesized which maintains the resistant state. 

Lehmann, K.P., Phillips, S., and Sar, M. et al. (2004). Dose-dependent alterations in gene expression and testosterone synthesis in the fetal testes of male rats exposed to di (n-butyl) phthalate. Toxicological Sciences 81, 60-68. 

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