Developmental Genetics of Corolla Tube Formation: Role of the tasiRNA- ARF Pathway and a Conceptual Model

• Published in: The Plant cell 2020-11, Vol.32 (11), p.3452-3468
• Main Authors: Ding, Baoqing, Xia, Rui, Lin, Qiaoshan, Gurung, Vandana, Sagawa, Janelle M, Stanley, Lauren E, Strobel, Matthew, Diggle, Pamela K, Meyers, Blake C, Yuan, Yao-Wu
• Format: Article
• Language: English
• Subjects: Arabidopsis Proteins - genetics; Flowers - anatomy & histology; Flowers - drug effects; Flowers - genetics; Flowers - growth & development; Gene Expression Regulation, Plant; Indoleacetic Acids - metabolism; Metabolic Networks and Pathways - genetics; Mimulus - drug effects; Mimulus - genetics; Mimulus - growth & development; Mutation; Phenotype; Phthalimides - pharmacology; Plant Proteins - genetics; Plants, Genetically Modified; RNA, Plant - genetics; RNA, Small Interfering
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.18.00471

Over 80,000 angiosperm species produce flowers with petals fused into a corolla tube. The corolla tube contributes to the tremendous diversity of flower morphology and plays a critical role in plant reproduction, yet it remains one of the least understood plant structures from a developmental genetics perspective. Through mutant analyses and transgenic experiments, we show that the tasiRNA- pathway is required for corolla tube formation in the monkeyflower species Loss-of-function mutations in the orthologs of and cause a dramatic decrease in abundance of -derived small RNAs and a moderate upregulation of ( ) and , which lead to inhibition of lateral expansion of the bases of petal primordia and complete arrest of the upward growth of the interprimordial regions, resulting in unfused corollas. Using the auxin-responsive promoter, we discovered that auxin signaling is continuous along the petal primordium base and the interprimordial region during the critical stage of corolla tube formation in the wild type, similar to the spatial pattern of expression. Auxin response is much weaker and more restricted in the mutant. Furthermore, exogenous application of a polar auxin transport inhibitor to wild-type floral apices disrupted petal fusion. Together, these results suggest a new conceptual model highlighting the central role of auxin-directed synchronized growth of the petal primordium base and the interprimordial region in corolla tube formation.