Physic nut (Jatropha curcas L.) is a perennial plant that belongs to the Euphorbiaceae family and is a potential oilseed plant for the production of renewable biofuel. The APETALA1 (AP1) was identified as a floral meristem identity gene to regulate flowering in many plant species. However, the function analysis of AP1 gene in Jatropha has not been reported.

    Prof. XU Zengfu and his team of Xihshuangbanna Tropical Botanical Garden (XTBG) cloned and characterized a Jatropha AP1homolog, JcAP1, through genetic complementation of the Arabidopsis AP1loss-of-function mutant ap1-11. They analyzed the function of JcAP1 in flowering induction and floral organ specification using transgenic Arabidopsis and Jatropha plants.

    A combined reverse transcriptase-polymerase chain reaction (RT-PCR) strategy was used to isolate AP1-like cDNA (JcAP1) from Jatropha. Amino acid sequence similarity, protein structures, and phylogenetic analysis suggested that JcAP1 exhibits a similar function to other AP1 homologues. 

To assess the expression pattern of JcAP1 in Jatropha, they performed a qRT-PCR analysis using RNA extracted from the roots, stems, mature leaves, inflorescence buds, flower buds, male flowers, female flowers and fruits. Quantitative RT-PCR results showed that JcAP1 transcripts were highly expressed in inflorescence buds, flower buds, sepals and petals.

Overexpression of JcAP1 in the Arabidopsis ap1-11 mutant resulted in early flowering, restoration of sepal and petal development, and repression of secondary flower formation in the bract axils. The expression profiles revealed that the highestJcAP1 transcript levels occurred in the earlier stages of male and female flower buds. The high JcAP1 expression levels observed in sepals and petals suggested that JcAP1 may be involved in sepal and petal development.

 They showed that overexpression ofJcAP1 in Arabidopsis resulted in reduced vegetative growth, early flowering and the formation of terminal and solitary flowers. Therefore, JcAP1 is an ortholog of AtAP1, which plays a similar role in the regulation of flowering in Arabidopsis, but may be insufficient to regulate flowering by itself in Jatropha.

 The study entitled “Ectopic expression of Jatropha curcas APETALA1 (JcAP1) caused early flowering in Arabidopsis, but not in Jatropha” has been published in PeerJ.