Indeterminate growth of the umbel inflorescence and bulb is associated with increased expression of the TFL1 homologue, AcTFL1, in onion

• Published in: Plant science (Limerick) 2019-10, Vol.287, p.110165-110165, Article 110165
• Main Authors: Dalvi, Vijayendra S., Patil, Yogesh A., Krishna, Bal, Sane, Prafullachandra V., Sane, Aniruddha P.
• Format: Article
• Language: English
• Subjects: Alliaceae; Bulbing; Cloning, Molecular; Gene Expression Regulation, Plant; Genes, Plant - genetics; Indeterminacy; Inflorescence - growth & development; Inflorescence - metabolism; Onions - genetics; Onions - growth & development; Onions - metabolism; Phylogeny; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots - growth & development; Plant Roots - metabolism; Real-Time Polymerase Chain Reaction; Sequence Alignment; TERMINAL FLOWER1; Transcriptome; Umbel; Vernalization
• ISSN: 0168-9452; 1873-2259
• DOI: 10.1016/j.plantsci.2019.110165

•AcTFL1 is expressed in the meristem-containing tissues of bulb and umbel in onion.•Its expression increases with indeterminate growth of the umbel and the bulb.•Its expression is lowest in the outer layers and highest in the inner bulb layers•AcTFL1 levels decrease upon bulb storage prior to flowering.•AcTFL1 complements the tfl1-14 mutant defect in Arabidopsis and delays flowering. TERMINAL FLOWER1 (TFL1) is a key gene for maintenance of vegetative and inflorescence indeterminacy and architecture. In onion, flowering and bulbing are two distinct developmental phases, each under complex environmental regulatory control. We have identified two CEN/TFL1-like genes from onion designated as AcTFL1 and AcCEN1. AcTFL1 is expressed during bulbing and inflorescence development with expression increasing with indeterminate growth of the umbel and the bulb suggesting possible conservation of function. Increase in AcTFL1 expression during umbel growth is associated with a simultaneous reduction in expression of AcLFY. Expression of AcTFL1 within the bulb is lowest in the outermost layers and highest in the innermost (youngest) layers. Bulb storage at room temperature or in cold leads to a gradual reduction in AcTFL1 levels in the meristem-containing tissues, the decrease being faster in the variety not requiring vernalization. Constitutive expression of AcTFL1, but not AcCEN1 complements the Arabidopsis tfl1-14 mutant and delays flowering in wild type suggesting conservation of the AcTFL1 function even in the distantly related Arabidopsis. Taken together, AcTFL1 appears to be the functional counterpart of TFL1 and regulates indeterminate growth of the umbel inflorescence as well as bulb development in onion.