The cytological basis of self-incompatibility in goji (Lycium barbarum) and the cloning of S-RNase gene.

Abstract

Main conclusion: Goji displays characteristics of gametophytic self-incompatibility. The S-RNase gene, expressed in the style, serves as the S determinant in the pistil, playing a key role in regulating goji's self-incompatibility. Goji, a plant commonly found worldwide, has been traditionally used for medicinal and culinary purposes in Chinese culture. However, breeding this species is challenging due to its self-incompatibility (SI). This study utilized 'Ningqi 1', 'Ningqi 6', and 'Ningqi 8', which exhibit significant variations in SI, as the experimental subjects. Detailed observations of floral organs and artificial pollination trials were conducted to elucidate the SI traits among different goji cultivars. Furthermore, the crucial pistil S factor that mediates SI in goji has been successfully cloned and subjected to analysis. The study revealed that goji exhibits gametophytic self-incompatibility (GSI). 'Ningqi 1' has a facultative selfing breeding system, while 'Ningqi 6' and 'Ningqi 8' involve facultative cross-pollination. Four S-RNase genes were successfully cloned from goji plants. Differential expression analysis revealed exclusive expression of S-RNase genes in the style. 'Ningqi 8' had significantly higher expression of the S₂-RNase gene compared to the S₁-RNase gene, suggesting that the S₂-RNase gene may play a pivotal role in regulating the SI mechanism of 'Ningqi 8'. This research provides insights into the cytological mechanisms of SI in goji, informing the planning of pollination tree arrangements and the selection of parental stocks for self-compatible breeding programs. It also lays the groundwork for future molecular studies on SI in goji.