Identification of a novel self-compatible phenotype and its mutant SRK allele harbourin an LTR-retrotransposon in radish (Raphanus sativus L.)

ABSTRACT

Self-incompatibility (SI) responses of radish (Raphanus sativus L.) are determined by two tightly linked genes encoding an S receptor kinase (SRK) and an S-locus cysteine-rich protein/S locus protein 11 (SCR/SP11), respectively. A radish showing an almost self-compatible (SC) phenotype was identified in this study. Inheritance patterns showed that this SC phenotype was dominant over an SI phenotype. In addition, the SC phenotype co-segregated with an S haplotype in an F₂ population. This SC radish contained an RsS-26 haplotype in which duplicate SRK-like genes were previously identified. Full-length sequences of two SRK-like genes of 18,133-bp and 6,200-bp in length were obtained, and they were designated as RsSRK-26-1 and RsSRK-26-2, respectively. No critical mutation was found in the coding region of SRK-like genes. However, a 4,146-bp intact LTR-retrotransposon was identified in the third intron of RsSRK-26-1 of the SC radish. Interestingly, this LTR-retrotransposon was not detected in three other breeding lines containing the same RsS-26 haplotype. While normal transcription of RsSRK-26-1 and SI phenotypes were observed in these three breeding lines, no transcript of RsSRK-26-1 was detected in the SC radish, suggesting that recent transposition of an LTR-retrotransposon in the RsSRK-26-1 gene might be responsible for the SC phenotype of radish.

KEYWORDS:

• Radish (Raphanus sativus L.)
• self-incompatibility
• S haplotype
• self-compatible mutant
• duplicate SRK genes

Acknowledgments

The authors thank Ji-hwa Heo, Jeong-An Yoo, and Su-jeong Kim for their dedicated technical assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability

Nucleotide sequences of SRK and SCR/SP11 alleles obtained in this study are accessible at NCBI Database.

Supplementary material

Supplemental data for this article can be accessed here

Additional information

Funding

This research was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (iPET) through a Golden Seed Project [Center for Horticultural Seed Development, No 213007-05-5-SBB10] and a grant from the Next-Generation BioGreen 21 Program [Plant Molecular Breeding Center No. PJ011034].