Genetic Diversity of Genes Controlling Unilateral Incompatibility in Japanese Cultivars of Chinese Cabbage

Abstract

In recent years, unilateral incompatibility (UI), which is an incompatibility system for recognizing and rejecting foreign pollen that operates in one direction, has been shown to be closely related to self-incompatibility (SI) in Brassica rapa. The stigma- and pollen-side recognition factors (SUI1 and PUI1, respectively) of this UI are similar to those of SI (stigma-side SRK and pollen-side SP11), indicating that SUI1 and PUI1 interact with each other and cause pollen-pistil incompatibility only when a specific genotype is pollinated. To clarify the genetic diversity of SUI1 and PUI1 in Japanese B. rapa, here we investigated the UI phenotype and the SUI1/PUI1 sequences in Japanese commercial varieties of Chinese cabbage. The present study showed that multiple copies of nonfunctional PUI1 were located within and in the vicinity of the UI locus region, and that the functional SUI1 was highly conserved in Chinese cabbage. In addition, we found a novel nonfunctional SUI1 allele with a dominant negative effect on the functional SUI1 allele in the heterozygote.

Stop and go signals at the stigma–pollen interface of the Brassicaceae

“…An unusual case of intraspecific UI was observed in crosses between self-incompatible strains of B. rapa from Japan and Turkey. Contrary to the expectation that these strains would be cross-compatible because of the different S haplotypes they express, the stigmas of the Japanese line reject pollen from the Turkish line while the stigmas of the Turkish line accept pollen from the Japanese line ( Takada et al 2021 ). Interestingly, this UI system was found to be based on the activity of tightly linked SRK -like and SCR -like genes that were apparently produced by duplication of the bona fide S locus and subsequent translocation of the duplicated segment to a new genomic location.…”

“…Interestingly, this UI system was found to be based on the activity of tightly linked SRK -like and SCR -like genes that were apparently produced by duplication of the bona fide S locus and subsequent translocation of the duplicated segment to a new genomic location. In this case, intraspecific UI is explained by the occurrence of stochastic mutations which inactivated the stigma SRK- like gene in Turkish strains and the pollen SCR- like gene in Japanese strains ( Takada et al 2021 ).…”

Unilateral cross-incompatibility between Camellia oleifera and C. yuhsienensis provides new insights for hybridization in Camellia spp

“…UCI and SI are potentially linked in some flowering plants ( Lewis and Crowe, 1958 ; Hancock et al., 2003 ), but it is unknown in genus Camellia . Many species have yielded such findings on the mechanism of hybridization disorder recently of UCI and SI ( He et al., 2019 ; Takada et al., 2021 ; Wang et al., 2022 ), but the molecular mechanism of cross-incompatibility in genus Camellia still requires further elucidation to provide insights for overcoming the reproductive barriers among genus Camellia species, and to propose reliable methods to overcome as well.…”

MLPK function is not required for self-incompatibility in the S29 haplotype of Brassica rapa L.

“…The degree of compatibility (compatibility score; CS) in each test pollination was scored on a five-point scale based on pollen tube penetration as follows: (CS = 5) penetration of more than 10 pollen tubes into the style; (CS = 4) penetration of 1–10 pollen tubes into the style; (CS = 3) penetration of pollen tubes into papilla cells but not into the style; (CS = 2) germination of pollen but no pollen-tube penetration into papilla cells; (CS = 1) no germination of pollen. Average scores less than 3 were defined as incompatible, and scores 3 and above as compatible (Takada et al 2017 ; 2021 ). Stigmas from at least three flowers for each cross combination were tested and this was replicated on at least five different dates.…”