Abstract
Transcription factors of the APETALA 2/Ethylene Response Factor (AP2/ERF)- family have been implicated in diverse processes during development, stress acclimation and retrograde signaling. Fifty-three leaf-expressed AP2/ERFs were screened for their transcriptional response to abscisic acid (ABA), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), methylviologen (MV), sucrose and high or low light, respectively, and revealed high reactivity to these effectors. Six of them (AP2-2, ARF14, CEJ1, ERF8, ERF11, RAP2.5) were selected for combinatorial response analysis to ABA, DCMU and high light. Additive, synergistic and antagonistic effects demonstrated that these transcription factors are components of multiple signaling pathways. AP2-2 (At1g79700) was subjected to an in depth study. AP2-2 transcripts were high under conditions linked to limited carbohydrate availability and stress and down-regulated in extended light phase, high light or in the presence of sugar. ap2-2 knock out plants had unchanged metabolite profiles and transcript levels of co-expressed genes in extended darkness. However, ap2-2 revealed more efficient germination and faster early growth under high sugar, osmotic or salinity stress, but the difference was abolished in the absence of sugar or during subsequent growth. It is suggested that AP2-2 is involved in mediating starvation-related and hormonal signals.
Highlights
Plants encounter stress if abiotic growth parameters severely deviate from optimum and during adverse biotic interactions
The aim of this work was to address the involvement of Apetala 2 transcription factor (AP2)/ERF-transcription factors (TFs) in the integration of signaling pathways that possibly are implicated in the retrograde control of nuclear gene expression
The starting point of our work was to investigate the possible involvement of APETALA 2/Ethylene Response Factor (AP2/ERF)-TFs in nuclear responses to retrograde signaling
Summary
Plants encounter stress if abiotic growth parameters severely deviate from optimum and during adverse biotic interactions. AP2/ERF-TFs are found outside the plant kingdom [7] In plants they are involved in signaling processes, e.g., ABI4 affects abscisic acid (ABA), redox and sugar signaling and acts downstream of genomes uncoupled 1 (GUN1) [8]. Another TF of this family, RRTF1, strongly responds to environmental stresses like high light [9]. DREB1A and DREB2A mediate transcriptional responses to cold, drought and salinity. DREB1A was found to be cold-responsive and DREB2A drought-responsive, respectively [10] Both TFs function in two different signaling pathways despite their high similarity. Despite good knowledge on some AP2/ERF-TFs, the functions of most group members remain elusive
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