Action of the Style Product of the Self-Incompatibility Gene of Nicotiana alata (S-RNase) on in Vitro-Grown Pollen Tubes.

AUTOR(ES)

Gray, JE

RESUMO

The products of the S-locus expressed in female tissues of Nicotiana alata are ribonucleases (S-RNases). The arrest of growth of incompatible pollen tubes in styles may result from entry of the S-RNase into the pollen tube and degradation of pollen tube RNA. We investigated the action of isolated S-RNases on pollen tubes grown in vitro and found that S-RNase is taken up by the pollen without substantial alteration. The S-RNases inhibit incorporation of exogenously added radioactive amino acids into protein by the germinated pollen. The S-RNases also inhibit in vitro translation of pollen tube RNA in a wheat germ cell-free extract. We found no evidence for a specific mRNA substrate for the S-RNases, which implies that if RNase activity is involved in the control of self-incompatibility, allelic specificity is more likely to depend on the selective uptake of S-RNases into pollen tubes or their selective activation or inactivation by pollen factors, rather than cleavage of a specific substrate. Heat treating S2-RNase largely destroys its RNase activity but increases its inhibitory effect on in vitro pollen tube growth. This effect is not due to an increased uptake of S2-RNase by the pollen but is associated with a greatly enhanced accumulation of S2-RNase on the outer surface of the pollen grains.

Documentos Relacionados

• Effect on in Vitro Pollen Growth of an Isolated Style Glycoprotein Associated with Self-Incompatibility in Nicotiana alata1
• S-RNase gene of Nicotiana alata is expressed in developing pollen.
• Identification, isolation, and N-terminal sequencing of style glycoproteins associated with self-incompatibility in Nicotiana alata.
• Sequence variability of three alleles of the self-incompatibility gene of Nicotiana alata.
• Expression of a Self-Incompatibility Glycoprotein (S2-Ribonuclease) from Nicotiana alata in Transgenic Nicotiana tabacum.