Transcriptome profiling provides new insights into florets number difference of inflorescence in L.angustifolia

Background: Lavender flowers essential oil had been used for a variety of therapeutic and cosmetic purposes, and had been popular for centuries. The previous studies of lavender mainly focused on essential oil composition and extraction methods, ignoring the factors that affected the production of essential oils, such as the floret number. This study aims to get a deep insight into the mechanism of florets number difference. Results: 1.Hormone profile showed positive correlation between ABA content and the number of florets, while IAA was negatively correlated. 2. RNA-Seq results showed that 2848 differentially expressed genes (DEG) were screened by comparing different florets samples in one plant. By analyzing dynamic changes of differentially expressed genes, many potentially interesting genes that encoded putative regulators or key components of ABA metabolism and signaling transduction were identified, such as NCED , PYL , PP2C , SnRK2 . 3.Common network analysis showed that the key genes of ABA pathway metabolism were negatively related to the DEG of IAA, especial IAA18. 4. Exogenous IAA significantly inhibited the number of lavender florets and affected the expression of ABA pathway metabolism genes, such as NCED, PP2C . Conclusions: 1. The different concentrations of ABA lead to florets number difference in the L.angustifolia “JX-2” clusters; 2. ABA may affect the florets number by regulating IAA transport and accumulation.The results will be useful for a better understanding of the molecular mechanism on florets number difference, which will lay the foundation for molecular breeding of muti-flortes varieties.