Abstract
The role of many genes and interactions among genes involved in flowering time have been studied extensively in Arabidopsis, and the purpose of this study was to investigate how effectively results obtained with the model species Arabidopsis can be applied to the Brassicacea with often larger and more complex genomes. Brassica rapa represents a very close relative, with its triplicated genome, with subgenomes having evolved by genome fractionation. The question of whether this genome fractionation is a random process, or whether specific genes are preferentially retained, such as flowering time (Ft) genes that play a role in the extreme morphological variation within the B. rapa species (displayed by the diverse morphotypes), is addressed. Data are presented showing that indeed Ft genes are preferentially retained, so the next intriguing question is whether these different orthologues of Arabidopsis Ft genes play similar roles compared with Arabidopsis, and what is the role of these different orthologues in B. rapa. Using a genetical–genomics approach, co-location of flowering quantitative trait loci (QTLs) and expression QTLs (eQTLs) resulted in identification of candidate genes for flowering QTLs and visualization of co-expression networks of Ft genes and flowering time. A major flowering QTL on A02 at the BrFLC2 locus co-localized with cis eQTLs for BrFLC2, BrSSR1, and BrTCP11, and trans eQTLs for the photoperiod gene BrCO and two paralogues of the floral integrator genes BrSOC1 and BrFT. It is concluded that the BrFLC2 Ft gene is a major regulator of flowering time in the studied doubled haploid population.
Highlights
In flowering plants, the change from vegetative to reproduc- Controlling the timing of this transition is especially importive development is a major transition that is sensitive to vari- tant in crop plants as it determines the geographical range ous seasonal climatic signals (Andres and Coupland, 2012). where the crop can be cultivated and ensures high agricultural4504 | Xiao et al.productivity
Data are presented showing that flowering time (Ft) genes are preferentially retained, so the intriguing question is whether these different orthologues of Arabidopsis Ft genes play similar roles compared with Arabidopsis, and what is the role of these different orthologues in B. rapa
A total of 768 B. rapa genes were identified in a screen of expressed sequence tag (EST), bacterial artificial chromosome (BAC), and Chinese cabbage genome sequences as homologues of 365 genes involved in flowering in Arabidopsis (Table 1; Supplementary Table S1 at JXB online)
Summary
The change from vegetative to reproduc- Controlling the timing of this transition is especially importive development is a major transition that is sensitive to vari- tant in crop plants as it determines the geographical range ous seasonal climatic signals (Andres and Coupland, 2012). where the crop can be cultivated and ensures high agricultural4504 | Xiao et al.productivity. The change from vegetative to reproduc- Controlling the timing of this transition is especially importive development is a major transition that is sensitive to vari- tant in crop plants as it determines the geographical range ous seasonal climatic signals (Andres and Coupland, 2012). Genetic factors that control flowering time are well studied in the model plant Arabidopsis. Control of flowering in Arabidopsis is the result of an interaction of environmental and physiological factors in different pathways: the vernalization pathway, photoperiod/circadian clock pathway, autonomous pathway, ageing pathway, ambient temperature pathway, and gibberellin pathway (Roux et al, 2006; Alonso-Blanco et al, 2009; Fornara et al, 2010). Comparative genetic and physical mapping and genome sequencing studies have confirmed the syntenic relationship between Arabidopsis and the triplicated genome of B. rapa, with subgenomes having evolved by genome fractionation (Park et al, 2005; Wang et al, 2011; Cheng et al, 2012; Tang et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
