Daniel K. Dzidzienyo, Glenn J. Bryan, Gail Wilde, Timothy P. Robbins

Theoretical and Applied Genetics; October 2016, Volume 129, Issue 10, pp 1985–2001

Key message

The S-ribonuclease sequences of 16 S-alleles derived from diploid types of Solanum are presented. A phylogenetic analysis and partial phenotypic analysis support the conclusion that these are functional S-alleles.

Abstract

S-Ribonucleases (S-RNases) control the pistil specificity of the self-incompatibility (SI) response in the genus Solanum and several other members of the Solanaceae. The nucleotide sequences of S-RNases corresponding to a large number of S-alleles or S-haplotypes have been characterised. However, surprisingly, few S-RNase sequences are available for potato species. The identification of new S-alleles in diploid potato species is desirable as these stocks are important sources of traits such as biotic and abiotic resistance. S-RNase sequences are reported here from three distinct diploid types of potato: cultivated Solanum tuberosum Group Phureja, S. tuberosum Group Stenotomum, and the wild species Solanum okadae. Partial S-RNase sequences were obtained from pistil RNA by RT-PCR or 3′RACE (Rapid Amplification of cDNA Ends) using a degenerate primer. Full-length sequences were obtained for two alleles by 5′RACE. Database searches with these sequences identified 16 S-RNases in total, all of which are novel. The sequence analysis revealed all the expected features of functional S-RNases. Phylogenetic analysis with selected published S-RNase and S-like-RNase sequences from the Solanaceae revealed extensive trans-generic evolution of the S-RNases and a clear distinction from S-like-RNases. Pollination tests were used to confirm the self-incompatibility status and cross-compatibility relationships of the S. okadae accessions. All the S. okadae accessions were found to be self-incompatible as expected with crosses amongst them exhibiting both cross-compatibility and semi-compatibility consistent with the S-genotypes determined from the S-RNase sequence data. The progeny analysis of four semi-compatible crosses examined by allele-specific PCR provided further confirmation that these are functional S-RNases.

Communicated by Y. Xue.

See: http://link.springer.com/article/10.1007/s00122-016-2754-7

Fig. 5   Phylogenetic tree of S-RNases and S-like RNases. A phylogenetic tree of the 16 cloned S-RNases and selected S-like Rnases from Solanaceae. Three published S-RNases, one from each of Petunia,  Nicotiana and  Solanum chaoense (highlighted with a  triangle) were included as reference sequences. Fungal RNase T2 of Aspergillus oryzae was included as an out-group to root the phylo-genetic tree. Numbers are bootstrap values expressed as a percentage and only those exceeding 50  % are shown. Bootstrap values were based on 1000  replicates. The phylogenetic tree was drawn using MEGA5 software. N.ala  =  Nicotiana alata, N.glu  =  Nicotiana glutinosa, N.tab  =  Nicotiana tabacum, S.lyc  =  Solanum lycopersicon, S.oka  =  Solanum okadae, S.phu  =  Solanum phureja, S.ste  =  Solanum stenotomum