Multi-omics comprehensive analysis of fruitlet abscission mechanism after self-pollination of Akebia trifoliata ssp. australis

【Objective】In this study,multi-omics comprehensive analysis methods were used to explore the mechanism of fruitlet abscission after self-pollination of Akebia trifoliata ssp. australis,and to provide a theoretical basis for the breeding of improved varieties of A. trifoliata ssp. australis. 【Method】Self-pollination and interspecific pollination of A.trifoliata ssp. australis cultivated variety BMTGKAN1 were carried out by artificial pollination techniques. Samples were taken on the 13^rd and 18^th d after pollination. The pollen tube germination was analyzed by aniline blue staining method, and ovule development was observed by paraffin section technique, and the retention rate of fruitlet under different pollination treatments was calculated. The mechanism of fruitlet shedding after pollination was analyzed by transcriptome and metabolome.The germination and growth of pollen in BMTGKAN1 pisticles were similar between self-pollinated and cultivated varieties. However, during fertilization, the ovule of cultivated interspecific pollination occurred nuclear fusion at 6 h after pollination. The ovule area of self-pollination group was small, and nuclear fusion did not occur. 【Result】At 18 d after pollination,the ovules of inter-specific pollination developed endosperm and embryo,while the ovules of selfpollination developed no endosperm and embryo,and the inner and outer integuments were separated,and the fruitlet retention rate was quite different at this time. On the ¹⁸th d after pollination,the fruitlet retention rate of self-pollinated was only 5.92%,while that of cultivated species was as high as 86.24%. At the level of transcription and metabolism,compared with self-pollination,there were 444 and 3646 differential expressed genes(DEGs) and 427 and 412 differential metabolites(DEMs) on the 13^rd and 18^th d after pollination. In the comparison of the same pollination methods,there were 3305 DEGs and 457 DEMs on the ¹³rd d after self-pollination compared with the 18^th d after self-pollination. There were 1123 DEGs and 420 DEMs in inter-species pollination. The results of real-time fluorescence quantitative PCR showed the same trend as the transcriptome data, indicating that the transcriptome data analysis results were relatively accurate. In the joint analysis of DEGs and DEMs in each comparison group,a total of 162 KEGG metabolic pathways were enriched in at least one comparison group,of which 48 were enriched in each comparison group. Metabolic pathways such as plant hormone signal transduction,linoleic acid metabolism,ABC transporters,and phenylpropanoid biosynthesis were likely to be involved in regulating the abscission of fruitlets after self-pollination of A. trifoliata ssp. australis. 【Conclusion】BMTGKAN1 belongs to late self-incompatibility plant, its fruitlets of A. trifoliata ssp. australis will all fall off within 13-18 d after self-pollination, and regulated by pathways of plant hormone signal transduction,linoleic acid metabolism,ABC transporters,phenylpropanoid biosynthesis. It is suggested that at least two varieties of A. trifoliata ssp. australis with similar flowering period should be selected for interlaced cross planting to improve fruit setting rate.