Characterization of self-incompatible Brassica napus lines lacking SP11 expression

Area of Science:

• Plant reproductive biology
• Genetics and molecular biology
• Brassica research

Background:

• Self-incompatibility (SI) in Brassicaceae is primarily regulated by the S-receptor kinase (SRK) and SP11 genes.
• While Brassica rapa and B. oleracea are self-incompatible, cultivated Brassica napus often exhibits self-compatibility due to its hybrid origin.
• The precise mechanisms governing SI in different B. napus lines remain incompletely understood.

Purpose of the Study:

• To investigate the S haplotypes, SI phenotypes, and SP11 gene expression in diverse B. napus lines.
• To identify the genetic basis for self-incompatibility in B. napus lines that appear to lack functional SP11 expression.
• To explore potential novel factors regulating self-incompatibility in B. napus.

Main Methods:

• Confirmation of S haplotypes and SI phenotypes in 10 representative B. napus lines.
• Analysis of SP11 gene expression patterns.
• Identification and characterization of insertions in the promoter regions of SP11 genes using molecular techniques.

Main Results:

• Two self-incompatible B. napus lines (N110 and N343) were identified with absent SP11 expression.
• A 3.6-kb insertion in the BnSP11-1 promoter was found in N343, correlating with suppressed BnSP11-1 and BnSP11-6 expression.
• A 4.3-kb insertion in the BnSP11-9 promoter was identified in N110, alongside suppressed expression of BnSP11-6, BnSP11-8, and BnSP11-9, potentially due to other S haplotypes.

Conclusions:

• The study identified self-incompatible B. napus lines exhibiting SI phenotypes despite the absence of SP11 gene expression.
• Insertions in SP11 promoter regions can disrupt gene expression, leading to altered self-incompatibility mechanisms.
• These findings suggest the involvement of unknown genetic or regulatory factors in inducing pollen-stigma incompatibility in B. napus, beyond the canonical SRK-SP11 pathway.