Abstract
For floral induction in adult citrus, low temperature is one of the most important environmental factors. FLOWERING LOCUS C (FLC) plays a very important role in low-temperature-induced Arabidopsis flowering by repressed FLC expression under exposure to prolonged low-temperature conditions. However, little is known about the FLC regulation mechanism in perennial woody plants such as citrus. In this study, the functions of citrus FLC homolog (PtFLC) were investigated by ectopic expression in Arabidopsis. Transcription factor of homeodomain leucine zipper I (HD-ZIP I) as an upstream regulator of PtFLC was identified by yeast one-hybrid screen to regulate its transcription. The HD-ZIP I transcription factor was highly homologous to Arabidopsis ATHB13 and thus was named PtHB13. Ectopically expressed PtHB13 inhibited flowering in transgenic Arabidopsis. Furthermore, the expression of PtFLC and PtHB13 showed a seasonal change during the floral induction period and was also affected by low temperature. Thus, we propose that PtHB13 binds to PtFLC promoter to regulate its activity during the citrus floral induction process.
Highlights
Floral induction and flowering are among the most crucial events in the plant life cycle because they must occur at in an appropriate time to ensure seed survival and subsequent germination [1,2]
Since FLOWERING LOCUS C (FLC) is a MADS-box transcription factor, we suspected that PtFLC may act a master regulator of flowering by influencing the expression of numerous genes
Vernalization describes the ability to promote flowering after prolonged exposure to low temperature [1]
Summary
Floral induction and flowering are among the most crucial events in the plant life cycle because they must occur at in an appropriate time to ensure seed survival and subsequent germination [1,2]. It has been well known that several factors affect floral induction and flowering of plants, including autonomous and environmental factors [2]. Five flowering pathways (photoperiod, gibberellin, vernalization, age, and endogenous) have been identified in model plants [3,4]. Many floral induction, development and blooming related genes have been characterized in model plants. Among these genes, FLOWERING LOCUS T (FT), FLOWERING LOCUS C (FLC), SUPRESSOR OF OVEREXPRESSION OF. Some putative homologs of these genes have been isolated and characterized in perennial woody plants [4,5]. The relatively poor mechanism for the regulation of these genes were related to woody plants compared with model plants
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