Celestina Mariani

Developmental expression of tobacco pistil-specific genes encoding novel extensin-like proteins.

We have sought to identify pistil-specific genes that can be used as molecular markers to study pistil development. For this purpose, a cDNA library was constructed from poly(A)+ RNA extracted from tobacco stigmas and styles at different developmental stages. Differential screening of this library led to the isolation of cDNA clones that correspond to genes preferentially or specifically expressed in the pistil. Seven of these cDNA clones encode proteins containing repetitions of the pentapeptide Ser-Pro4, which is a typical motif found in extensins. Unlike extensin genes, the extensin-like genes described here are not induced under stress conditions. RNA gel blot hybridizations demonstrated the organ-specific expression of the extensin-like genes and their temporal regulation during pistil development. After pollination, the transcript levels of the pistil-specific extensin-like genes change relative to levels in unpollinated pistils. In situ hybridization experiments showed that at least one of these pistil-specific genes is specifically expressed in cells of the transmitting tissue. The possible roles of the extensin-like proteins in pistils are discussed.

Isolation of Genes Preferentially Expressed in Pistils of Tobacco Flowers

Flowering is a complex process which begins with the conversion of a vegetative meristem into a floral meristem. Cells divide and differentiate to develop a structure which contains different organ types organized as whorls, occupying precisely determined positions. From outside to inside, the flower is composed of the sterile organs (sepals and petals) and fertile organs (stamens and carpels or pistils).