Expression of subtilisin-like serine proteases in Arabidopsis thaliana is cell-specific and responds to jasmonic acid and heavy metals with developmental differences

The expression of two novel subtilisin-like serine proteases At-SLP2 and At-SLP3 from Arabidopsis thaliana and the recently identified Arabidopsis subtilase ARA12 was analysed with respect to plant development, stress response and cell specificity. In juvenile plants the mRNAs of the subtilisin-like proteases At-SLP2, At-SLP3 and ARA12 were detected with varying transcript levels in leaves but not in roots. In mature Arabidopsis plants transcripts were abundant in leaves, roots and flowers revealing developmental regulation of synthesis of subtilases. By in situ hybridization it was shown that the subtilisin-like proteases were predominantly present in epidermal cells and in the vascular bundles, in the phloem and in developing xylem elements. In flowers additional signals were localized, for example, in pistils, ovules and anthers. In flowers and juvenile developing leaves, expression of the subtilisin-like proteases increased following treatment with jasmonate and cadmium, respectively, suggesting that these proteases are responsive to stress and pathogen stimuli. The physiological relevance of these data in relation to plant morphogenesis and development is discussed.