Reduced Expression of CbUFO Is Associated with the Phenotype of a Flower-Defective Cosmos bipinnatus.

Fei Li,Qin Zhou,Wu Lan,Feng Chen,Guofeng Liu,Manzhu Bao,Sisi Zhang,Baojun Liu

doi:10.3390/ijms20102503

Abstract

LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) homologous genes have been reported to play key roles in promoting the initiation of floral meristems in raceme- and cyme-type plants. Asteraceae, a large family of plants with more than 23,000 species, has a unique head-like inflorescence termed capitulum. Here, we report a floral defective plant of the garden cosmos named green head (gh), which shows homogeneous inflorescence, indistinguishable inflorescence periphery and center, and the replacement of flower meristems by indeterminate inflorescence meristems, coupled with iterative production of bract-like organs and higher order of inflorescences. A comparison of the LFY- and UFO-like genes (CbFLY and CbUFO) isolated from both the wild-type and gh cosmos revealed that CbUFO may play an important role in inflorescence differentiation into different structures and promotion of flower initiation, and the reduced expression of CbUFO in the gh cosmos could be associated with the phenotypes of the flower-defective plants. Further expression analysis indicated that CbUFO may promote the conversion of inflorescence meristem into floral meristem in early ray flower formation, but does not play a role in its later growth period.

Highlights

Flower initiation and development, two pivotal events during the life cycle of flowering plants, play a key role in the reproductive fitness of plants, as well as the successful production of crops
In Asteraceae plants, the phenotype of the gh showed the loss of floral organ identities and repetitive initiation of inflorescence primordia, with the secondary and tertiary inflorescence primordia subtended by bract-like structures, which is especially similar to the phenotype of severe RNAi transgenic lines of GhLFY and GhUFO and the GhUFO-lacking mutant “PingPong” described in Gerbera [18]
Given that the role of LFY and UNUSUAL FLORAL ORGANS (UFO) homologous genes in flower development regulation have been confirmed in most angiosperms, such as Asteraceae plants, and that the gh phenotype is not derived from the coding sequences (CDS) mutation of the CbLFY or CbUFO gene, the decrease of CbUFO expression can be assumed to be responsible for the absence of the floral organ phenotype in cosmos

Summary

Introduction

Two pivotal events during the life cycle of flowering plants, play a key role in the reproductive fitness of plants, as well as the successful production of crops. Except for a single flower, three basic architectural types of inflorescence have been proposed based on the activity of the inflorescence meristem in initiating lateral branches and the timing of its transition to floral meristems: raceme, cyme, and panicle [5,6]. Most inflorescences found in nature can be grouped into one of these three broad categories [7] Plants such as Arabidopsis thaliana and Antirrhinum majus develop the raceme-type inflorescences, with main inflorescence axes growing indefinitely and bearing flowers in lateral positions or lateral axes that reiterate this pattern. Petunia and tomato develop the cyme-type inflorescences, in which the main inflorescence meristems terminate in a flower after producing a new inflorescence meristem that reiterates this pattern. Unlike the raceme- or cyme-type inflorescences, the panicle-type inflorescence is extensively branched and is largely characteristic of grasses, such as oat and rice [6,7]

Methods

Findings

Discussion

Conclusion