Multiple gene co-options underlie the rapid evolution of sexually deceptive flowers in Gorteria diffusa.

Gene co-option, the redeployment of an existing gene in an unrelated developmental context, is an important mechanism underlying the evolution of morphological novelty. In most cases described to date, novel traits emerged by co-option of a single gene or genetic network. Here, we show that the integration of multiple co-opted genetic elements facilitated the rapid evolution of complex petal spots that mimic female bee-fly pollinators in the sexually deceptive South African daisy Gorteria diffusa. First, co-option of iron homeostasis genes altered petal spot pigmentation, producing a color similar to that of female pollinators. Second, co-option of the root hair gene GdEXPA7 enabled the formation of enlarged papillate petal epidermal cells, eliciting copulation responses from male flies. Third, co-option of the miR156-GdSPL1 transcription factor module altered petal spot placement, resulting in better mimicry of female flies resting on the flower. The three genetic elements were likely co-opted sequentially, and strength of sexual deception in different G. diffusa floral forms strongly correlates with the presence of the three corresponding morphological alterations. Our findings suggest that gene co-options can combine in a modular fashion, enabling rapid evolution of novel complex traits.

Keep a distance to be different: axillary buds initiating at a distance from the shoot apical meristem are crucial for the perennial lifestyle of Arabis alpina.

In many seed plants, perennialism is achieved through axillary buds and side shoots that remain vegetative. This work aimed to analyse the pattern of axillary bud (AB) formation in the perennial model plant Arabis alpina and to study the role of the LATERAL SUPPRESSOR (AaLAS) gene. This study combines stereomicroscopic analysis with RNA sequencing to monitor the correlation between patterns of AB formation and gene expression. The role of AaLAS was studied using an RNA interference (RNAi) approach. During vegetative development, ABs initiate at a distance from the shoot apical meristem (SAM), whereas after floral induction, they initiate adjacent to the SAM. Dormant buds are established before the onset of vernalization. Transcript profiles of ABs initiated at a distance differed from those in the SAM, whereas those of buds initiated in close proximity were similar. Knockdown of AaLAS leads to the loss of dormant buds and vegetative side shoots, strongly compromising the perennial life cycle. AB formation is regulated differently during vegetative and reproductive development. New meristems that possess different gene expression profiles from those in the SAM are established at a distance from the SAM. AaLAS is essential for the perennial life cycle by modulating the establishment of dormant buds and vegetative side shoots.