Evolutionary and functional analysis of mulberry type III polyketide synthases

Abstract

BackgroundType III polyketide synthases are important for the biosynthesis of flavonoids and various plant polyphenols. Mulberry plants have abundant polyphenols, but very little is known about the mulberry type III polyketide synthase genes. An analysis of these genes may provide new targets for genetic improvement to increase relevant secondary metabolites and enhance the plant tolerance to biotic and abiotic stresses.ResultsEighteen genes encoding type III polyketide synthases were identified, including six chalcone synthases (CHS), ten stilbene synthases (STS), and two polyketide synthases (PKS). Functional characterization of four genes representing most of the MnCHS and MnSTS genes by coexpression with 4-Coumaroyl-CoA ligase in Escherichia coli indicated that their products were able to catalyze p-coumaroyl-CoA and malonyl-CoA to generate naringenin and resveratrol, respectively. Microsynteny analysis within mulberry indicated that segmental and tandem duplication events contributed to the expansion of the MnCHS family, while tandem duplications were mainly responsible for the generation of the MnSTS genes. Combining the evolution and expression analysis results of the mulberry type III PKS genes indicated that MnCHS and MnSTS genes evolved mainly under purifying selection to maintain their original functions, but transcriptional subfunctionalization occurred during long-term species evolution. Moreover, mulberry leaves can rapidly accumulated oxyresveratrol after UV-C irradiation, suggesting that resveratrol was converted to oxyresveratrol.ConclusionsCharacterizing the functions and evolution of mulberry type III PKS genes is crucial for advancing our understanding of these genes and providing the basis for further studies on the biosynthesis of relevant secondary metabolites in mulberry plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2843-7) contains supplementary material, which is available to authorized users.

Identification and validation of reference genes for qRT-PCR analysis in mulberry (Morus alba L.)

“…and tung ( Vernicia fordii ) [ 33 , 34 ] but is not a suitable reference gene in Arabidopsis thaliana and Rhododendron [ 35 , 36 ]. TUB s are considered to be the best reference genes in water lily and soybean [ 37 , 38 ] but are not stably expressed in Rhododendron [ 35 ]. GAPDH , EF-1α , and UBI are involved in biochemical metabolic processes in organisms and are traditional reference genes in plants [ 31 , 32 ].…”

Flavones Produced by Mulberry Flavone Synthase Type I Constitute a Defense Line against the Ultraviolet-B Stress

“…qRT-PCRs were completed using a StepOnePlus Real-Time PCR System (Applied Biosystems, Foster City, CA, USA). The program conditions and reaction mixture were set as described by Li et al [51]. The mulberry ACTIN3 gene was used as an internal control.…”

Regulation of stilbene biosynthesis in plants

“…The expressional analyses of the STS gene family members in grapevine and mulberry revealed that some STS genes exhibit differences in transcriptional responses during development and in response to environmental stresses (Vannozzi et al 2012;Shi et al 2014;Dai et al 2012). There were also differences in tissue-specific expression of some grapevine and mulberry STS gene family members (Vannozzi et al 2012;Shi et al 2014;Li et al 2016). Therefore, it is possible that distinct STS genes can be activated under various developmental or environmental cues or in different plant tissues leading to accumulation of stilbenes.…”

“…The available literature data demonstrate that STS genes in sorghum, spruce, pine, peanut, and mulberry form small gene families composed of 1-10 members (Preisig-Müller et al 1999;Yu et al 2005;Paterson et al 2009;Zhu et al 2014;Warren et al 2015;Li et al 2016), while STS gene family in grapevine consists of 48 STS genes with at least 32 potentially functional ones as revealed by the genomewide analysis of the grapevine genome (Vannozzi et al 2012;Parage et al 2012). Functional analysis of nine STS genes representing most diversity of the STS gene family in grapevine performed by Parage et al (2012) revealed that the genes encode proteins possessing STS activity.…”