PT  - JOURNAL ARTICLE
AU  - Baoqing Ding
AU  - Rui Xia
AU  - Vandana Gurung
AU  - Janelle M. Sagawa
AU  - Lauren E. Stanley
AU  - Matthew Strobel
AU  - Qiaoshan Lin
AU  - Pamela K. Diggle
AU  - Blake C. Meyers
AU  - Yao-Wu Yuan
TI  - Developmental genetics of corolla tube formation: role of the tasiRNA-ARF pathway
AID  - 10.1101/253112
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 253112
4099  - http://biorxiv.org/content/early/2018/01/24/253112.short
4100  - http://biorxiv.org/content/early/2018/01/24/253112.full
AB  - More than 80,000 angiosperm species produce flowers with petals fused into a corolla tube (i.e., sympetalous flowers). 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. Importantly, by integrating the molecular and phenotypic analyses of the tasiRNA-ARF pathway in Mimulus with historical insights from morphological and anatomical studies in various sympetalous species, we propose a new conceptual model for the developmental genetic control of corolla tube formation. This model offers logical connections among the sporadic previous reports of corolla tube mutants in other species and makes clear predictions that can be readily tested using the Mimulus system.