Antisense inhibition of a tomato meiotic proteinase suggests functional redundancy of proteinases during microsporogenesis

Anther development in angiosperms culminates in the programmed cell death of specific tissues to facilitate the release of pollen. Despite a wealth of morphological descriptions of this process, there have been few reports on the regulation of dehiscence or the coordination of events between tissues. We have cloned an anther-specific tomato gene encoding a serine proteinase that is expressed during meiosis and late microsporogenesis. The conceptualized tomato meiotic proteinase (TMP) is a member of a family of genes that exhibit characteristics of mammalian proprotein convertases. To examine the role of TMP in microsporogenesis, we generated transgenic plants harboring an antisense construct of the gene. Some of these plants produced little or no detectable TMP, yet no phenotypic abnormalities were observed. Zymogram analyses revealed that multiple proteinases are present in mature anthers and that proteinase activity increases as development proceeds. Taken together, these data indicate that the role of TMP during microsporogenesis, if any, may be compensated for by other proteinases.