Petal Patterns

Joint work with Joshua Puzey and Arielle Cooley at Whitman College.

Life on earth exhibits a dazzling array of patterns, from internal repeated structures such as vertebrae to external pigment patterns such as stripes. Two broad ideas explain how these patterns can form. In a positional specification model, genes are turned on in specific locations in a controlled fashion. In a reaction-diffusion model, patterns arise from a self-organizing system of interacting genes, where random fluctuations in one gene’s activity can be amplified by the response of other genes in the network.

Petal spots in the monkeyflower genus Mimulus appear to depend on both positional specification and reaction-diffusion mechanisms. This project uses the petal-spot system to study how those mechanisms interact to create new and complex patterns in nature.

Previous work in Mimulus established that nectar-guide spots of red anthocyanin pigment form in a way that is consistent with a reaction-diffusion system. The discovery of elaborate spot patterns in petal lobes of Mimulus cupreus x M. luteus var. variegatus hybrids creates an opportunity to ask whether this reaction-diffusion system explains floral patterning more generally, whether positional cues from petal vasculature shape these patterns, and how hybridization can generate novel phenotypes absent from either parent species.

The project develops reaction-diffusion models that reproduce anthocyanin spotting phenotypes observed in hybrid genetic mapping populations. These models are tested against homozygous genotypes in Recombinant Inbred Lines and against experiments that alter expression of key genes in the anthocyanin regulatory network. A related aim is to determine whether petal vasculature influences spot location using digital image analysis, spatial statistics, and experimental perturbations of vein development.

Prior Work

• Kinser TJ, Smith RD, Lawrence AH, Cooley AM, Vallejo-Marin M, Conradi Smith GD, and Puzey JR. Mechanisms driving endosperm-based hybrid incompatibilities: insights from hybrid monkeyflowers. Plant Cell. [10.1105/tpc.17.00010] [BioRxiv preprint]
• Zheng X, Om K, Stanton KA, Thomas D, Schlutius C, Cheng PA, Eggert A, Simmons E, Yuan Y-W, Conradi Smith GD, Puzey JR*, Cooley AM*. MYB5a/NEGAN activates petal anthocyanin pigmentation and shapes the MBW regulatory network in Mimulus luteus var. variegatus. Genetics. [10.1093/genetics/iyaa036]
• Smith RD, Kinser TJ, Conradi Smith GD and Puzey JR. A likelihood ratio test for changes in homeolog expression bias. BMC Bioinformatics 20:149, 2019. [doi:10.1186/s12859-019-2709-5] [PMID:30894122] [BioRxiv preprint]
• Edger PP, Smith RD, McKain MR, Cooley AM, Vallejo-Marin M, Yuan Y, Bewick AJ, Ji L, Platts AE, Bowman MJ, Childs KL, Schmitz RJ, Smith GD, Pires JC, Puzey JR. Subgenome dominance in an interspecific hybrid, synthetic allopolyploid, and a 140 year old naturally established neo-allopolyploid monkeyflower. The Plant Cell 29(9):2150-2167, 2017. [doi:10.1105/tpc.17.00010] [PMID:28814644]