Biology subjects

Yuan, Y.-W.

Publications and source records attributed to Yuan, Y.-W..

3 recordsLinked to original sources

bioRxiv2018

Formation of periodic pigment spots by the reaction-diffusion mechanism

Many organisms exhibit visually striking spotted or striped pigmentation patterns. Turings reaction-diffusion model postulates that such periodic pigmentation patterns form when a local autocatalytic feedback loop and a long-range inhibitory feedback loop interact. At its simplest, this network only requires one self-activating activator that also activates a repressor, which inhibits the activator and diffuses to neighboring cells. However, the molecular activators and repressors fully fitting this versatile model remain elusive. Here, we characterize an R2R3-MYB activator and an R3-MYB repressor in monkeyflowers that correspond to Turings model and explain how periodic anthocyanin spots form. Notably, disrupting this pattern impacts pollinator visitation. Thus, subtle changes in simple reaction-diffusion networks are likely essential contributors to the evolution of the remarkable diversity of periodic pigmentation patterns in flowers.

plant biology↗

bioRxiv2018

Developmental genetics of corolla tube formation: role of the tasiRNA-ARF pathway

More than 80,000 angiosperm species produce flowers with petals fused into a corolla tube. As an important element of the tremendous diversity of flower morphology, the corolla tube plays a critical role in many specialized interactions between plants and animal pollinators (e.g., beeflies, hawkmoths, hummingbirds, nectar bats), which in turn drives rapid plant speciation. Despite its clear significance in plant reproduction and evolution, the corolla tube remains one of the least understood plant structures from a developmental genetics perspective. Through mutant analyses and transgenic experiments, here we show that the tasiRNA-ARF pathway is required for corolla tube formation in the monkeyflower species Mimulus lewisii. Loss-of-function mutations in the M. lewisii orthologs of ARGONAUTE7 and SUPPRESSOR OF GENE SILENCING 3 cause a dramatic decrease in abundance of TAS3-derived small RNAs and a moderate up-regulation of AUXIN RESPONSE FACTOR 3 (ARF3) and ARF4, which lead to inhibition of lateral expansion of the bases of petal primordia and complete arrest of the upward growth of the inter-primordial regions, resulting in unfused corollas. By using an auxin reporter construct, we discovered that auxin distribution is continuous along the petal primordium base and the inter-primordial region during the critical stage of corolla tube formation in the wild-type, and that this auxin distribution is much weaker and more restricted in the mutant. Together, these results suggest a new conceptual model highlighting the central role of auxin directed synchronized growth of the petal primordium base and the inter-primordial region in corolla tube formation.

plant biology↗

bioRxiv2017

A Tetratricopeptide Repeat Protein Regulates Carotenoid Biosynthesis and Chromoplast Development in Monkeyflowers (Mimulus)

The incredible diversity of floral color and pattern in nature is largely determined by the transcriptional regulation of anthocyanin and carotenoid biosynthetic genes. While the transcriptional control of anthocyanin biosynthesis is well understood, little is known about the factors regulating the carotenoid biosynthetic pathway in flowers. Here, we characterize the Reduced Carotenoid Pigmentation 2 (RCP2) locus from two monkeyflower (Mimulus) species, the bumblebee-pollinated M. lewisii and hummingbird-pollinated M. verbenaceus. We show that loss-of-function mutations of RCP2 cause drastic down-regulation of the entire carotenoid biosynthetic pathway in these species. Through bulk segregant analysis and transgenic experiments, we have identified the causal gene underlying RCP2, encoding a tetratricopeptide repeat (TPR) protein that is closely related to the Arabidopsis Reduced Chloroplast Coverage (REC) proteins. RCP2 appears to regulate carotenoid biosynthesis independently of RCP1, a previously identified R2R3-MYB master regulator of carotenoid biosynthesis. We show that RCP2 is required for chromoplast development and suggest that it most likely regulates the expression of carotenoid biosynthetic genes through chromoplast-to-nucleus retrograde signaling. Furthermore, we demonstrate that M. verbenaceus is just as amenable to chemical mutagenesis and in planta transformation as the more extensively studied M. lewisii, making these two species an excellent platform for comparative developmental genetics studies of two closely related species with dramatic phenotypic divergence.

genetics↗