Transcriptomic analysis of nectar spur development

Nectar spurs (tubular outgrowths of the floral organ) have long fascinated biologists. However, given that no model species possess nectar spurs, there is still much to learn about their development. In this study, we combined morphological analysis with comparative transcriptomics to gain a global insight into the morphological and molecular basis of spur outgrowth in Linaria. RNA-Seq was performed on two closely related species at three key developmental stages, one with a spur (Linaria vulgaris), and one without a spur (Antirrhinum majus). A list of spur-specific genes was selected, on which we performed a gene enrichment analysis. Results from our RNA-seq analysis agreed with our morphological observations. For example, at an early stage, genes associated with cell division are highly expressed in the developing spur. At a later stage in spur development, genes associated with cell wall remodelling are expressed. Our list of spur-specific genes was enriched for genes connected to the plant hormones cytokinin, auxin and gibberellin. We present a global view of the genes involved in spur development in L. vulgaris, and define a suite of genes which are specific to spur development. This work provides a catalogue of candidate genes for spur outgrowth and development in L. vulgaris which can be investigated in future studies.