A homolog of the ALOG family controls corolla tube differentiation in .

Flowers of honey plants () face various abiotic stressors, including rain, that can damage pollens and dilute nectar. Many species are thought to have evolved a modified corolla base termed the corolla neck to prevent raindrops from contacting the nectar. Although this hypothesis was postulated long ago, direct validation is lacking. Here, we have evaluated , the corolla tube of which differentiates into distinct regions: a conical tube above that connects to an inflated base through a constriction. This constriction and inflated base are collectively referred to as the corolla neck. Using transcriptomic sequencing and genome-editing approaches, we have characterized an gene, , that is involved in formation of the corolla neck. was found expressed in the epidermis of the corolla neck. Cells in the corolla bottom differentiated and expanded in wild-type , whereas such cells in loss-of-function mutants failed to develop into a corolla neck. Water easily contacted the nectary in the absence of the corolla neck. Taken together, our study unveils a novel gene that controls corolla tube differentiation and demonstrates a hypothetical property of the corolla neck.