A genetic framework for flowering-time pathways in Citrus spp.

Marcelo Carnier Dornelas,Marco Aurélio Takita,Raquel Luciana Boscariol Camargo,Luciana Harumi Morimoto Figueiredo

doi:10.1590/s1415-47572007000500006

Marcelo Carnier Dornelas, Marco Aurélio Takita + Show 2 more

Open Access

https://doi.org/10.1590/s1415-47572007000500006

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Abstract

Floral transition is one the most drastic changes occurring during the life cycle of a plant. The shoot apical meristem switches from the production of leaves with associated secondary shoot meristems to the production of flower meristems. This transition is abrupt and generally irreversible, suggesting it is regulated by a robust gene regulatory network capable of driving sharp transitions. The moment at which this transition occurs is precisely determined by environmental and endogenous signals. A large number of genes acting within these pathways have been cloned in model herbaceous plants such as Arabidopsis thaliana. In this paper, we report the results of our search in the Citrus expressed sequence tag (CitEST) database for expressed sequence tags (ESTs) showing sequence homology with known elements of flowering-time pathways. We have searched all sequence clusters in the CitEST database and identified more than one hundred Citrus spp sequences that codify putative conserved elements of the autonomous, vernalization, photoperiod response and gibberelic acid-controlled flowering-time pathways. Additionally, we have characterized in silico putative members of the Citrus spp homologs to the Arabidopsis CONSTANS family of transcription factors.

Highlights

When grown from seeds, Citrus seedlings progress through a developmental ontogeny typical for woody perennials, eventually producing a moderately sized tree
The field of flowering time has been organized around these four pathways, with the photoperiod and vernalization pathways mediating the response to environmental cues and the autonomous and the gibberellin (GA) pathways acting largely independently of these external signals (Figure 1)
Based on the systematic search in the Citrus expressed sequence tag (CitEST) database using Arabidopsis sequences as bait, we have identified 109 Citrus spp

Summary

Introduction

When grown from seeds, Citrus seedlings progress through a developmental ontogeny typical for woody perennials, eventually producing a moderately sized tree. Typically lasting several years, Citrus trees enter the adult phase in which they are capable of continuously producing flowers in addition to vegetative shoots (Krajewski and Rabe, 1995). Flowers can potentially be produced throughout the year, but in most oranges and mandarins grown in temperate environments, the majority of flowers are produced during the spring flush. Pollination, fertilization and seed development are required for fruit set, while in others, parthenocarpic fruit development can occur. In some cases this is stimulated by pollination (Koltunow et al, 2000)

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