Journal Article

Overexpression of PaNAC03, a stress induced NAC gene family transcription factor in Norway spruce leads to reduced flavonol biosynthesis and aberrant embryo development

Wind, Julia Johanna, Ezcurra, Ines, Nemesio-Gorriz, Miguel, Dalman, Kerstin, Hammerbacher, Almuth, Lundén, Karl, Elfstrand, Malin

2017

Overview

Background The NAC family of transcription factors is one of the largest gene families of transcription factors in plants and the conifer NAC gene family is at least as large, or possibly larger, as in Arabidopsis . These transcription factors control both developmental and stress induced processes in plants. Yet, conifer NACs controlling stress induced processes has received relatively little attention. This study investigates NAC family transcription factors involved in the responses to the pathogen Heterobasidion annosum (Fr.) Bref. sensu lato. Results The phylogeny and domain structure in the NAC proteins can be used to organize functional specificities, several well characterized stress-related NAC proteins are found in III-3 in Arabidopsis (Jensen et al. Biochem J 426:183–196, 2010). The Norway spruce genome contain seven genes with similarity to subgroup III-3 NACs. Based on the expression pattern PaNAC03 was selected for detailed analyses. Norway spruce lines overexpressing PaNAC03 exhibited aberrant embryo development in response to maturation initiation and 482 misregulated genes were identified in proliferating cultures. Three key genes in the flavonoid biosynthesis pathway: a CHS, a F3’H and PaLAR3 were consistently down regulated in the overexpression lines . In accordance, the overexpression lines showed reduced levels of specific flavonoids, suggesting that PaNAC03 act as a repressor of this pathway, possibly by directly interacting with the promoter of the repressed genes. However, transactivation studies of Pa NAC03 and PaLAR3 in Nicotiana benthamiana showed that Pa NAC03 activated PaLAR3A, suggesting that PaNAC03 does not act as an independent negative regulator of flavan-3-ol production through direct interaction with the target flavonoid biosynthetic genes. Conclusions PaNAC03 and its orthologs form a sister group to well characterized stress-related angiosperm NAC genes and at least PaNAC03 is responsive to biotic stress and appear to act in the control of defence associated secondary metabolite production.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V
• Subject: Agriculture / Arabidopsis / ATAF (Arabidopsis transcription activation factor) / ATAF1 / Bark / Biochemistry and physiology / Bioflavonoids / Biomedical and Life Sciences / Biosynthesis / biotic stress / conifers / CUC (cup-shaped cotyledon) / embryogenesis / Embryonic development / Embryos / Evergreen trees / Flavones / Flavonoids / Flavonoids - biosynthesis / flavonols / Forest Science / Gene expression / Gene Expression Regulation, Plant / gene overexpression / genes / Genetic aspects / Heterobasidion / Heterobasidion annosum / Homeodomain proteins / Leucoanthocyanidin reductase (LAR) / Life Sciences / Metabolites / Multigene Family / NAC [for NAM (no apical meristem) / Nicotiana benthamiana / Norway / pathogens / Phylogeny / Picea / Picea - classification / Picea - embryology / Picea - genetics / Picea - metabolism / Picea abies / Pine trees / Plant Proteins - genetics / Plant Proteins - metabolism / Plant Sciences / Research Article / Resistance to Heterobasidion annosum / secondary metabolites / Skogsvetenskap / transcription (genetics) / transcription factors / Transcription Factors - genetics / Transcription Factors - metabolism / transcriptional activation / Transcriptome / Tree Biology