Transcriptomics Investigation into the Mechanisms of Self-Incompatibility between Pin and Thrum Morphs of Primula maximowiczii

Abstract

Heteromorphic self-incompatibility (SI) is an important system for preventing inbreeding in the genus Primula. However, investigations into the molecular mechanisms of Primula SI are lacking. To explore the mechanisms of SI in Primula maximowiczii, the pollen germination and fruiting rates of self- and cross-pollinations between pin and thrum morphs were investigated, and transcriptomics analyses of the pistils after pollination were performed to assess gene expression patterns in pin and thrum SI. The results indicated that P. maximowiczii exhibits strong SI and that the mechanisms of pollen tube inhibition differ between pin and thrum morphs. While self-pollen tubes of the pin morph were able to occasionally, though rarely, enter the style, those of the thrum morph were never observed to enter the style. The transcriptomics analysis of the pistils revealed 1311 and 1048 differentially expressed genes (DEGs) that were identified by comparing pin self-pollination (PS) vs. pin cross-pollination (PT) and thrum self-pollination (TS) vs. thrum cross-pollination (TP). Notably, about 90% of these DEGs exhibited different expression patterns in the two comparisons. Moreover, pin and thrum DEGs were associated with different Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways following enrichment analyses. Based on our results, the molecular mechanisms underlying the pin and thrum SI in P. maximowiczii appear to be distinct. Furthermore, the genes involved in the SI processes are commonly associated with carbohydrate metabolism and environmental adaptation. These results provide new insight into the molecular mechanisms of Primula SI.

Comparative stigmatic transcriptomics reveals self and cross pollination responses to heteromorphic incompatibility in Plumbago auriculata Lam.

“…In our study, DEGs in the MAPK (plant) signalling pathway were downregulated in “T × P” vs. “T × T” but exhibited the opposite trend in“P × T” vs. “P × P” ( Table 4 ). The identification of female S determinants, such as SRK in Brassica and Arabidopsis for SSI, and SI S1 in Papaver for GSI, along with critical components like PGAP1, in our results ( Goring et al, 2023 ), suggests that P. auriculata combines both SSI and GSI characteristics, similar to another HetSI species, Primula maximowiczii ( Lu et al, 2018 ). HetSI in pin flowers may share pathways with Arabidopsis SSI, where decreased MAPKs in “T × P” vs. “T × T” could inhibit MAPKs - Exo70A1 interaction and reduce pistil receptivity.…”

The rapid appearance of homostyly in a cultivated distylous population of Primula forbesii

“…To determine the pollen tube growth rate, each pollination type included 35 flowers from at least seven plants with five flowers fixed in 50% FAA for 12h per time interval (4, 8, 12, 24, 48, 96, and 144 h). After washing three times with distilled water, the styles were cleared in 8 mol L −1 NaOH solution at 25°C for 20 min, then rinsed three times again with distilled water before dying with 0.1% aniline blue for 25 min (Lu et al, 2018 ). More than 10 pollen tubes of each flower were then measured in transparent pistil tissue by fluorescence microscope (BX53‐DP80; Olympus).…”

Pollen Tube and Plant Reproduction

“…Information is also lacking on the mechanism of self-incompatibility in Primula. Lu et al analyzed pollen germination and fructification in the case of self and non-self crosses, and evaluated the levels of transcriptomics [7]. In addition to differences in the growth ability of pollen tubes, transcriptomic analyses showed a high number of differentially expressed genes, including genes associated with carbohydrate metabolism and environmental adaptation.…”