Comparative transcriptome analysis between ‘Meiguicheng’ (Citrus sinensis) and its seedless mutant during early sexual organs development

Female sterility is one of the keys determining seedlessness formation in citrus. However, the molecular basis for female sterility in citrus is still far from fully understood. In the present study, differentially expressed genes were identified in sexual organs of ‘Meiguicheng’ orange (Citrus sinensis) and its seedless mutant, candidate genes were then verified by RT-PCR, live-cell imaging technique and physiological biochemistry. Using high-throughput sequencing, 96 and 710 differentially expressed genes (DEGs) were captured in the ovaries and anthers, respectively, during megasporogenesis and microsporogenesis (Ph1). The number of DEGs in ovaries and anthers increased to 325 and 1760, respectively, post gametophyte abortion (Ph2). GO analysis and non-structural carbohydrates determination displayed that disturbances to starch and sucrose metabolism in anthers were responsible for male sterility. In Ph1 ovaries, five DEGs were enriched in reproduction process, one of which (Cs7g06410) was also involved in signaling. Whereas in Ph2 ovaries, eight DEGs were enriched in reproductive process, accompanied with four other DEGs involved in plant hormone signal transduction. PlantTFDB prediction indicated that, in the ovary, four transcription factors (TFs) at Ph1 were differentially expressed. Our findings displayed that Cs2g16620 (PIN1), Cs7g06410 (NPH3), and Cs3g23070 (MYB) might play pivotal roles in citrus female sterility through manipulating auxin transport and accumulation within the ovules, providing potential genes for further investigations on female gametophyte development and transgenic breeding in citrus.