A full-length genomic clone of 2,233 bp long containing an anther- and tapetum-specific gene TomA108 was isolated and characterized from tomato. The gene was present in one copy per haploid genome. The isolated clone contained 5' and 3' untranslated regions of 810 and 170 nucleotides, respectively and a single intron with highly repetitive sequences. The cDNA encoded the protein with an apparent mass of 10.6 kDa and a pI (isoelectric point) of 5.3. It was cysteine-rich and had an N-terminal hydrophobic domain with characteristics of a secretory signal. Amino acid sequence comparisons demonstrated that the protein was closely related to a family of cereal seed storage proteins and protease inhibitors. The fusion of beta-glucuronidase to the TomA108 promoter demonstrated that the promoter was highly active from early-meiosis to free microspores production in tapetum of tobacco. This strong and highly specific promoter can be potentially used to generate male sterility for efficient production of plant hybrids.
Flower longevity is an important character in many ornamental crops. The processes of pollination and fertilization can cause senescence of the petals through the action of ethylene or its precursors. Preventing the production of pollen and therefore pollination could delay the senescence of petals. We tested whether male-sterility would increase flower longevity in petunia. The gene consisted of a stamen-specific promoter isolated from a Lycopersicon esculentum gene driving the expression of a barnase. Barnase is a RNase that is cytotoxic. The gene was introduced into `Lavender Storm' and `Purple Wave' petunia by Agrobacterium- mediated gene transfer. Five independent transgenic lines of both cultivars were regenerated, rooted, and grown in a greenhouse. All lines showed complete male-sterility as measured by the lack of detectable pollen. Two transgenic lines and a non-transformed control of each cultivar were propagated vegetatively and the flower longevity of each genotype was determined in a greenhouse experiment. There were two treatments: no pollination or pollination with cross-compatible pollen. All sterile genotypes that were not pollinated had increased flower longevity relative to pollinated sterile flowers or either treatment of male fertile (non-transformed) genotypes. These results indicate an application for sterility in the production of petunia flowers with increased longevity. Male and female sterility may be applicable in other ornamental crops where pollination or fertilization is a trigger to petal senescence.
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