Novel self-compatible lines of Brassica rapa L. isolated from the Japanese bulk-populations

Abstract

Self-incompatibility (SI) in Brassicaceae is sporophytically controlled by a single Slocus with multi allelic variety. The male S determinant, SP11/SCR (S-locus protein 11/S-locus cysteine-rich protein), is a small cysteine-rich protein, and the female S determinant, SRK (S-locus receptor kinase), functions as a receptor for SP11 at the surface of stigma papilla cells. Although a few of the following downstream factors in the SP11-SRK signaling cascade have been identified, a comprehensive understanding of the SI mechanism still remains unexplained in Brassicaceae. Analysis of self-compatible (SC) mutants is significant for understanding the molecular mechanism in SI reactions, thus we screened SC lines from a variety of Japanese bulk-populations of B. rapa vegetables. Two lines, TSC4 and TSC28, seem to have disruptions in the SI signaling cascade, while the other line, TSC2, seems to have a deficiency in a female S determinant, SRK. In TSC4 and TSC28, known SI-related factors, i.e. SRK, SP11, MLPK (M-locus protein kinase), THL (thioredoxin-h-like), and ARC1 (arm repeat containing 1), were expressed normally, and their expression levels were comparable with those in SI lines. On a B. rapa genetic linkage map, potential SC genes in TSC4 and TSC28 were mapped on linkage groups A3 and A1, respectively, whereas MLPK, ARC1, and THL were mapped on A3, A4, and A6, respectively. Although potential SC genes of TSC4 and MLPK were on the same linkage group, their positions were apparently independent. These results indicate that the SC genes of TSC4 and TSC28 are independent from the S-locus or known SI-related genes. Thus, the SC lines selected here have mutations in novel factors of the SI signaling cascade, and they will contribute to fill pieces in a signal transduction pathway of the SI system in Brassicaceae.

Involvement of MLPK Pathway in Intraspecies Unilateral Incompatibility Regulated by a Single Locus With Stigma and Pollen Factors

“…Several genetic studies of the variation in strength of the SI response have been reported (Hatakeyama et al 2010; Isokawa et al 2010), suggesting that there are several genetic factors regulating SI strength in Brassica . From the viewpoint of incompatibility strength, UI described here has a strong incompatible response, the same as in the rigid SI phenotype.…”

Self-incompatibility in Brassicaceae crops: lessons for interspecific incompatibility

“…These results suggest the involvement of auxin in the regulation of self-incompatibility. Further analysis of mutants, either those that occur in natural populations (Isokawa et al 2010) or those induced by mutagenic treatments (Strickler et al 2013, Tantikanjana et al 2009) will no doubt identify new components of the SRK-mediated signaling pathway and clarify the mechanism of the self-incompatibility response.…”

Genetic and tissue-specific RNA-sequencing analysis of self-compatible mutant TSC28 in <i>Brassica rapa</i> L. toward identification of a novel self-incompatibility factor

“…Plant materials and observation of pollen tube behavior on the stigma An SC mutant line, TSC28, which was identified by screening Japanese bulk populations of B. rapa vegetable varieties and partially characterized as a novel SC mutant line that is independent from the S-locus or known SI-related genes (Isokawa et al, 2010), was used. As a reference B. rapa SI line, an inbred line, Chiifu-401 (Osaka et al, 2013), was used.…”

“…To identify all components of the SRK downstream pathway, alternative plant material and/or methodology is necessary. Previ-ously, we identified two novel SC mutant lines (TSC4 and TSC28) in B. rapa (Isokawa et al, 2010), from a screening of bulk populations of Japanese traditional and commercial B. rapa vegetables. The putative SC gene of TSC28 was mapped on linkage group A1, while S-locus, MLPK, ARC1 and THL were mapped on A7, A3, A4 and A6, respectively.…”