The WRKY superfamily of plantThe WRKY superfamily of planttranscription factorstranscription factors

 Introduction

Wrky

▶ WRKY (pronounced‘worky’) proteins, a large family of transcriptional regulators that has to date only been found in plants.

▶ The WRKY domain is defined by the conserved amino acidsequence WRKYGQK at its N-terminal end, together with a novel zinc-finger-like motif

▶ Many WRKY proteins having a regulatory function in the response to pathogen infection and other stresses.

▶ levels of WRKY mRNA, protein and DNA-binding activity havebeen reported to be induced by infection with viruses oomycetes fungal elicitors9 Signaling substances such as salicylic acid

▶ Comparative expression studies with several AtWRKY genes also suggest that certain family members have a role in the regulation of senescence.

▶ Transcript levels of AtWRKY4, 6, 7 and 11 are enhanced in senescent leaves.

▶ W boxes have been described as positive cis-acting elements upregulating transcription.

1.group I : two WRKY domains group II: one WRKY domains group III: newly define group

2.(Pc)sweet potato (Ib), Arabidopsis (At), tobacco (Nt), cucumber (Cs) and wild oat (Af ).

WRKY domains are blacknuclear localization signals are blue leucine zippers are pink serine–threonine-rich regions are yellowyellow glutamine-rich regions are purple proline-rich regions are green acidic regions are red

Fig. Phylogenetic analysis of 58 members of the AtWRKY family.

  Results

Targets of AtWRKY6 regulation during plant senescence and pathogen defense

ABSTRACT In Arabidopsis, ▶ WRKY factors large gene family of plant-specific transcriptional regulators controlling several types of plant stress responses.

▶ we identified targets of the senescence- and defense-associated WRKY6 factor.

▶ WRKY6 was found to suppress its own promoter activity, indicating negative autoregulation.

▶ WRKY6 positively influenced the senescence- and pathogen defense- associated PR1 promoter activity, most likely involving NPR1 function.

▶ One novel identified target gene, SIRK, encodes a receptor-like protein kinase, whose developmental expression is strongly induced specifically during leaf senescence. SIRK is dependent on WRKY6 function.

▶ Senescing leaves of wrky6 knockout mutants showed a drastic reduction, green leaves of WRKY6 overexpression lines showed clearly elevated SIRK

▶ The SIRK gene promoter was activated by WRKY6 in vivo

The Plant Journal

En-1 transposon insertion

Figure 1.   Identification of wrky6 knockout mutants

Figure 2.   WRKY6 overexpression lines.

The Plant Journal

SAG:salicyilcacid glucoside

ELI:plant defence-Related gene

The Plant Journal

Figure 3.   Repressor activity of WRKY6.

promotor GUS

promotor WRKY Knock out gene

Knock out

promotor GUS

promotor WRKY overexpression

overexepression

Rhizobacterium

JA response

Ethylene response

Pathogen

SA JA responseNahG ethylene response

NPRnpr1

etr1

PDF1.2PRSDefensive compounds

ISR SAR

jar1

The Plant Journal

Figure . Nuclear localization of endogenous AtWRKY6.

The Plant Journal

  Figure 4.   Effect of WRKY6 overexpression on PR1 and NPR1.

Table 1.   cDNA-AFLP fragments and homologies to sequences in the Arabidopsis database

R:root transcripts.R1-R154P:aerieal part transcripts P1-P63

Figure 5.   Dependence of SIRK gene expression on WRKY6

Figure 6.   Specificity of the WRKY6-SIRK promoter interaction

NecroticPathogeninfection

Systemic signal

SA NPR1 SARGeneexpression

EnhancedPathogenresistance

WRKY6?

SIRK