Expression profiling and functional analysis of Populus WRKY23 reveals a regulatory role in defense

Abstract

Summary• WRKY transcription factors are key regulators that activate and fine-tune stress responses, including defense responses against pathogens. We isolated a poplar (Populus tremula × Populus alba) cDNA sequence, PtWRKY23, that encodes the ortholog of Arabidopsis WRKY23 and present the functional analysis of WRKY23, with emphasis on its potential role in resistance to rust infection.• To investigate the function of PtWRKY23, we examined PtWRKY23 expression after stress treatments by qRT-PCR and generated PtWRKY23-misexpressing plants. Transgenic plants were assessed for resistance to Melampsora rust and were analyzed using the poplar Affymetrix GeneChip ® and histological techniques to study the consequences of PtWRKY23 misexpression.• PtWRKY23 is rapidly induced by Melampsora infection and elicitor treatments and poplars overexpressing and underexpressing PtWRKY23 were both more susceptible to Melampsora infection than wild type. Transcriptome analysis of PtWRKY23 overexpressors revealed a significant overlap with the Melampsorainfection response. Transcriptome analysis also suggests that PtWRKY23 affects redox homeostasis and cell wall-related metabolism, which was confirmed by analyses that showed that PtWRKY23-misexpressing plants have altered peroxidase activity, apparent H 2 O 2 accumulation and lignin deposition.• Our results show that PtWRKY23 affects resistance to Melampsora infection and that this may be caused by deregulation of genes that disrupt redox homeostasis and cell wall metabolism.

Transcription factor WRKY23 assists auxin distribution patterns during Arabidopsis root development through local control on flavonol biosynthesis

“…Interestingly, TT7 was also found to be significantly up-regulated in a transcript profiling study of WRKY23-overexpressing poplar (Populus sp.) plants (34), suggesting that WRKY23 regulates this branch of flavonoid metabolism in divergent lineages of higher plants. Moreover, flavonols (more precisely, quercetin derivatives) accumulate at infection sites of plant-parasitic nematodes (35), where WRKY23 is highly expressed (20), justifying further investigation of TT7 as a putative target of WRKY23.…”

Genome-wide survey and characterization of the WRKY gene family in Populus trichocarpa

“…Since the first cloning and characterization of a WRKY cDNA in the sweet potato (Ipomoea batatas) (Ishiguro and Nakamura 1994), a large number of corresponding genes for WRKY proteins have been rapidly identified and characterized in other plant species, such as rice (Oryza sativa) (Wu et al 2005), Arabidopsis thaliana (Eulgem et al 2000), potato (Solanum tuberosum) (Dellagi et al 2000), barley (Hordeum vulgare) (Mangelsen et al 2008), cotton (Gossypium arboreum) (Xu et al 2004), desert legume (Retama raetam) (Pnueli et al 2002), pine (Pinus monticola) (Liu and Ekramoddoullah 2009), poplar (Populus tremula 9 Populus alba) (Levee et al 2009) and sunflower (Helianthus annuus) (Giacomelli et al 2010). To date, approximately 74 and 102 representatives have been identified in the fully sequenced Arabidopsis and rice genomes, respectively.…”

Flavan-3-ols Are an Effective Chemical Defense against Rust Infection

“…The binary vector was constructed following the method described by Levée et al (2009). The transformation of P. nigra NP1 by an RNAi construct was achieved following a protocol optimized for Populus canescens (Meilan and Ma, 2006).…”