An S RNase gene of Lycopersicon peruvianum L. is highly expressed in transgenic tobacco but does not affect self-incompatibility

Lycopersicon peruvianum has a gametophytic self-incompatibility (GSI) mecha nism controlled by a single genetic locus (S locus) with multiple alleles. S RNases, an allelic series of abundant stylar proteins, are products of th e S locus in L. peruvianum and other Solanaceous plants. We introduced a ge nomic clone for the S-11 RNase from L. peruvianum into a self-compatible sp ecies (Nicotiana tabacum) to examine if the expression pattern in the heter ologous plant mimics that in L. peruvianum. The resultant transgenic N. tab acum plants expressed the introduced gene at a high level in their styles, similar to the S-11 gene expression in L. peruvianum. The S-11 RNase gene w as expressed in the style at a similar stage of flower development in both the transgenic tobacco plants and L. peruvianum, suggesting that the regula tory mechanism for S RNase gene expression is operating in a self-compatibl e heterologous plant. However, the transgenic plants did not show any morph ological changes or altered pollination behaviour as a result of this expre ssion. Unexpectedly, the S-11 RNase transcript: was also found in developin g anthers and mature pollen of the transgenic plants although the expressio n level is much lower compared to that in stylar tissues. This expression p attern has not been observed in L. peruvianum.