Abstract
BackgroundRadish (Raphanus sativus L.) belongs to the family Brassicaceae, and is an economically important root crop grown worldwide. Flowering is necessary for plant propagation, but it is also an important agronomic trait influencing R. sativus fleshy taproot yield and quality in the case of an imbalance between vegetative and reproductive growth. There is currently a lack of detailed information regarding the pathways regulating the flowering genes or their evolution in R. sativus. The release of the R. sativus genome sequence provides an opportunity to identify and characterize the flowering genes using a comparative genomics approach.ResultsWe identified 254 R. sativus flowering genes based on sequence similarities and analyses of syntenic regions. The genes were unevenly distributed on the various chromosomes. Furthermore, we discovered the existence of R. sativus core function genes in the flowering regulatory network, which revealed that basic flowering pathways are relatively conserved between Arabidopsis thaliana and R. sativus. Additional comparisons with Brassica oleracea and Brassica rapa indicated that the retained flowering genes differed among species after genome triplication events. The R. sativus flowering genes were preferentially retained, especially those associated with gibberellin signaling and metabolism. Moreover, analyses of selection pressures suggested that the genes in vernalization and autonomous pathways were more variable than the genes in other R. sativus flowering pathways.ConclusionsOur results revealed that the core flowering genes are conserved between R. sativus and A. thaliana to a certain extent. Moreover, the copy number variation and functional differentiation of the homologous genes in R. sativus increased the complexity of the flowering regulatory networks after genome polyploidization. Our study provides an integrated framework for the R. sativus flowering pathways and insights into the evolutionary relationships between R. sativus flowering genes and the genes from A. thaliana and close relatives.
Highlights
Radish (Raphanus sativus L.) belongs to the family Brassicaceae, and is an economically important root crop grown worldwide
174 genes are believed to regulate flowering in the model plant Arabidopsis thaliana, which are involved in six major pathways [i.e., vernalization, photoperiod and circadian clock, ambient temperature, gibberellin (GA), age, and autonomous pathways] influencing the bolting or blooming process [1]
We focused on the 160 protein-coding genes to identify homologous R. sativus flowering genes
Summary
Radish (Raphanus sativus L.) belongs to the family Brassicaceae, and is an economically important root crop grown worldwide. Flowering is necessary for plant propagation, but it is an important agronomic trait influencing R. sativus fleshy taproot yield and quality in the case of an imbalance between vegetative and reproductive growth. Flowering is a necessary part of plant propagation, and the process from bolting to blooming is a crucial period for the transition of Brassicaceae plants from vegetative to reproductive growth. Characterizing the regulatory mechanisms underlying bolting and blooming may enable researchers to influence the balance between vegetative and reproductive growth, which may affect the yield and quality of Brassicaceae crops. 174 genes are believed to regulate flowering in the model plant Arabidopsis thaliana, which are involved in six major pathways [i.e., vernalization, photoperiod and circadian clock, ambient temperature, gibberellin (GA), age, and autonomous pathways] influencing the bolting or blooming process [1]. The genes regulating bolting and flowering vary among different crops
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