Ectopic expression of Jatropha curcas APETALA1 (JcAP1) caused early flowering in Arabidopsis, but not in Jatropha.

Mingyong Tang,Zeng-Fu Xu,Yan-Bin Tao

doi:10.7717/peerj.1969

Mingyong Tang, Zeng-Fu Xu + Show 1 more

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https://doi.org/10.7717/peerj.1969

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Abstract

Jatropha curcas is a promising feedstock for biofuel production because Jatropha oil is highly suitable for the production of biodiesel and bio-jet fuels. However, Jatropha exhibits a low seed yield as a result of unreliable and poor flowering. APETALA1 (AP1) is a floral meristem and organ identity gene in higher plants. The flower meristem identity genes of Jatropha have not yet been identified or characterized. To better understand the genetic control of flowering in Jatropha, an AP1 homolog (JcAP1) was isolated from Jatropha. An amino acid sequence analysis of JcAP1 revealed a high similarity to the AP1 proteins of other perennial plants. JcAP1 was expressed in inflorescence buds, flower buds, sepals and petals. The highest expression level was observed during the early developmental stage of the flower buds. The overexpression of JcAP1 using the cauliflower mosaic virus (CaMV) 35S promoter resulted in extremely early flowering and abnormal flowers in transgenic Arabidopsis plants. Several flowering genes downstream of AP1 were up-regulated in the JcAP1-overexpressing transgenic plant lines. Furthermore, JcAP1 overexpression rescued the phenotype caused by the Arabidopsis AP1 loss-of-function mutant ap1-11. Therefore, JcAP1 is an ortholog of AtAP1, which plays a similar role in the regulation of flowering in Arabidopsis. However, the overexpression of JcAP1 in Jatropha using the same promoter resulted in little variation in the flowering time and floral organs, indicating that JcAP1 may be insufficient to regulate flowering by itself in Jatropha. This study helps to elucidate the function of JcAP1 and contributes to the understanding of the molecular mechanisms of flower development in Jatropha.

Highlights

With the decreasing availability of fossil fuels and the deteriorating trend of environmental pollution, biodiesel has garnered significant attention as an alternative fuel (Mofijur et al, 2016)
How to cite this article Tang et al (2016), Ectopic expression of Jatropha curcas APETALA1 (JcAP1) caused early flowering in Arabidopsis, but not in Jatropha
Further analysis indicated that the promotion of flowering in the 35S:JcAP1 transgenic Arabidopsis mutant was correlated with a significant up-regulation of the flower meristem identity genes AtLFY, AtSOC1 and floral organ identity genes AtSEPs (Figs. 4J and 4K). These results demonstrate that the constitutive expression of JcAP1 complements the defect in floral organ development observed in the ap1-11 mutant; JcAP1 functions as an A-class gene in transgenic Arabidopsis

Summary

Introduction

With the decreasing availability of fossil fuels and the deteriorating trend of environmental pollution, biodiesel has garnered significant attention as an alternative fuel (Mofijur et al, 2016). Jatropha has been propagated as a unique plant with biodiesel potential because of its multipurpose value, high oil content, high biomass productivity, adaptability to marginal land under a variety of agro-climatic conditions, and non-competitiveness with food production (Akashi, 2012; Khalil et al, 2013; Pandey et al, 2012; Pua et al, 2011). The potential of Jatropha as a biofuel plant is limited by its low seed production (King et al, 2015). Unreliable and poor flowering is an important factor that contributes to low seed productivity in Jatropha (Divakara et al, 2010). The elucidation of the genetic basis of flowering in Jatropha would be helpful for the molecular breeding of high-yielding Jatropha cultivars

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