Flowering is a fundamental process in plant development. Flower evocation is the transition from the vegetative to the reproductive phase, when the specialization of apical meristems takes place. In plants, such as the Solanaceae, which present complete flowers, the meristematic cells in the most external first series bring out the sepals and those cells in the second series turn to be the petals; in the third series the cells become stamens and the cells in the innermost series give origin to carpels (ovaries, styles and stigmas). Floral organs have shown up recently in evolution and this event demanded the development of tissue-specific patterns for gene expression. Indeed, some of the pathogenesis related genes from Solanaceae, induced by infection or wounding in vegetative organs, show flower-specific patterns of transcription, with constitutive expression and the occurrence of temporal profiles of expression controlled by development being detected in healthy floral tissues. PR10a, SK2, Sp41 pathogenesis related genes and an adenosine:methyltransferase, possibly related to pathogenesis as well, are genes that follow the described tissue-specific patterns and are reviewed here. Hypothesis proposed to demonstrate the meanings of these mechanisms of gene expression are also presented.
flowering; Sp41; PR10a; SK2; methyltransferase
