Abstract
BackgroundPhysic nut (Jatropha curcas), an inedible oilseed plant, is among the most promising alternative energy sources because of its high oil content, rapid growth and extensive adaptability. Proteins encoded by MADS-box family genes are important transcription factors participated in regulating plant growth, seed development and responses to abiotic stress. However, there has been no in-depth research on the MADS-box genes and their roles in physic nut.ResultsIn our study, 63 MADS-box genes (JcMADSs) were identified in the physic nut genome, and classed into five groups (MIKCC, Mα, Mβ, Mγ, MIKC*) according to phylogenetic comparison with Arabidopsis homologs. Expression profile analysis based on RNA-seq suggested that many JcMADS genes had the strongest expression in seeds, and seven of them responded in leaves to at least one abiotic stressor (drought and/or salinity) at one or more time points. Transient expression analysis and a transactivation assay indicated that JcMADS40 is a nucleus-localized transcriptional activator. Plants overexpressing JcMADS40 did not show altered plant growth, but the overexpressing plants did exhibit reductions in grain size, grain length, grain width, 1000-seed weight and yield per plant. Further data on the reduced grain size in JcMADS40-overexpressing plants supported the putative role of JcMADS genes in seed development.ConclusionsThis study will be useful in order to further understand the process of MADS-box genes involved in regulating growth and development in addition to their functions in abiotic stress resistance, and will eventually provide a theoretical basis for the functional investigation and the exploitation of candidate genes for the molecular improvement of physic nut.
Highlights
Physic nut (Jatropha curcas), an inedible oilseed plant, is among the most promising alternative energy sources because of its high oil content, rapid growth and extensive adaptability
The open reading frame (ORF) lengths of 63 JcMADS genes ranged from 195 bp (JcMADS35) to 1164 bp (JcMADS34), potentially the proteins encoded would be from 64 to 387 amino acids; their GenBank accession numbers are given in Additional File 1
Expression profile of JcMADS genes under non-stressed growth condition To clarify the roles of the JcMADS in regulating physic nut development, we examined the expression profiles of JcMADS genes in roots, stem cortex, leaves, and seeds (S1 and S2) under non-stressed growth conditions based on data from RNA sequencing (RNA-seq) (Additional File 4 and Fig. 4)
Summary
Physic nut (Jatropha curcas), an inedible oilseed plant, is among the most promising alternative energy sources because of its high oil content, rapid growth and extensive adaptability. Proteins encoded by MADS-box family genes are important transcription factors participated in regulating plant growth, seed development and responses to abiotic stress. The regulation of plant growth, development and stress responses is complex and is coordinated by many mechanisms These mechanisms are under the control of many related genes acting through complex regulatory networks. In these processes, transcription factor (such as members of the MYB, HD-Zip, ARF, NAC, MADSbox, and ERF gene families) recognize cisregulatory elements present in the promoter regions of these genes, and regulate their expression so as to modulate a wide range of biochemical, physiological and developmental processes [1,2,3,4,5,6]. According to the similarities of amino acid sequences and structural features of the conserved domains, MADSdomain proteins in Arabidopsis can be classified into five groups (designated MIKCC, Mα, Mβ, Mγ, MIKC*) [9]
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