Microstructural Observation and Transcriptome Analysis of Pistil Abortion in ‘Li Guang’ Apricot

Abstract Background: ‘Li Guang’ apricot, a famous local variety, originated in Dunhuang city, Gansu Province,China. It has a long flowering period and a large amount of flowers, but serious pistil abortion has become one of the key factors affecting the fruit set, yield and quality. The distribution and regulation of hormones play an important role in signal molecules of flower abortion. The critical mechanisms of hormone metabolism and the expression levels of genes involved in these processes are, however, poorly understood. Results: To clarify the critical molecular mechanisms of hormone-induced abortion in apricot, normal and abortive flower buds were taken as materials, the pistil abortion of apricot flower was studied by paraffin section, and the RNA seq was used to identify the genes related to flowering regulation. The pistil style was lower than filament. Microstructure showed that the pollen grains of abortive flowers were decreased sharply, the ovaries shrunk and the ovule primordia developed stagnately. Through RNA-Seq, 6647 differentially expressed genes, including 2543 up-regulated and 4104 down-regulated genes, were identified. According to the KEGG Pathway, the pyruvate metabolism, plant hormone signal transduction, spliceosome, RNA transport, protein processing in endoplasmic reticulum and other metabolic pathways were significantly enriched. It revealed that AUX1, AUX / IAA, TIR1, ARF, GH3 and SAUR , vital genes displayed identical differential expression profiles to auxin transduction pathway, and ABF , SnRK2 , PP2C to abscisic acid, JAZ, MYC2 to jasmonic acid. The qRT-PCR assay with independent samples showed that the expression levels of these selected genes were basically consistent with RNA-Seq results. Conclusions : In the whole differentiate stage of flower, pistil abortion represent versatile style . In this process, the changes of hormones play an important role in pistil abortion, especially IAA,GA,and CTK. Related genes involved in hormones synthesis expression regulate the content of hormones and to adapt to the occurrence of pistil abortion under adversity. At the same time, the ethylene response signal factor ERF1/2 (DN70415) was up-regulated in normal flowers, which further indicated that ethylene might be the key regulatory factor affecting the abortion of ‘Liguang’ apricot flowers.