The nascent polypeptide-associated (NAC) complex was described in yeast as a heterodimer composed of two subunits, α and β, and was shown to bind to the nascent polypeptides newly emerging from the ribosomes. NAC function was widely described in yeast and several information are also available about its role in plants. The knock down of individual NAC subunit(s) led usually to a higher sensitivity to stress. In Arabidopsis thaliana genome, there are five genes encoding NACα subunit, and two genes encoding NACβ. Double homozygous mutant in both genes coding for NACβ was acquired, which showed a delayed development compared to the wild type, had abnormal number of flower organs, shorter siliques and greatly reduced seed set. Both NACβ genes were characterized in more detail-the phenotype of the double homozygous mutant was complemented by a functional NACβ copy. Then, both NACβ genes were localized to nuclei and cytoplasm and their promoters were active in many organs (leaves, cauline leaves, flowers, pollen grains, and siliques together with seeds). Since flowers were the most affected organs by nacβ mutation, the flower buds' transcriptome was identified by RNA sequencing, and their proteome by gel-free approach. The differential expression analyses of transcriptomic and proteomic datasets suggest the involvement of NACβ subunits in stress responses, male gametophyte development, and photosynthesis.

• Keywords
• Arabidopsis thaliana, chaperone, flower bud proteome, flower bud transcriptome, male gametophyte, nascent polypeptide-associated complex,
• MeSH
• Alleles MeSH
• Arabidopsis physiology   MeSH
• Phenotype MeSH
• Plants, Genetically Modified MeSH
• Homozygote MeSH
• Germination MeSH
• Flowers physiology   MeSH
• Molecular Chaperones genetics   metabolism   MeSH
• Mutation MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Proteomics methods   MeSH
• Gene Expression Regulation, Plant MeSH
• Seeds MeSH
• Transcriptome MeSH
• Plant Development * genetics   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Molecular Chaperones MeSH
• nascent-polypeptide-associated complex MeSH Browser
• Arabidopsis Proteins MeSH

KEY MESSAGE : bZIP TF network in pollen. Transcriptional control of gene expression represents an important mechanism guiding organisms through developmental processes and providing plasticity towards environmental stimuli. Because of their sessile nature, plants require effective gene regulation for rapid response to variation in environmental and developmental conditions. Transcription factors (TFs) provide such control ensuring correct gene expression in spatial and temporal manner. Our work reports the interaction network of six bZIP TFs expressed in Arabidopsis thaliana pollen and highlights the potential functional role for AtbZIP18 in pollen. AtbZIP18 was shown to interact with three other pollen-expressed bZIP TFs-AtbZIP34, AtbZIP52, and AtbZIP61 in yeast two-hybrid assays. AtbZIP18 transcripts are highly expressed in pollen, and at the subcellular level, an AtbZIP18-GFP fusion protein was located in the nucleus and cytoplasm/ER. To address the role of AtbZIP18 in the male gametophyte, we performed phenotypic analysis of a T-DNA knockout allele, which showed slightly reduced transmission through the male gametophyte. Some of the phenotype defects in atbzip18 pollen, although observed at low penetrance, were similar to those seen at higher frequency in the T-DNA knockout of the interacting partner, AtbZIP34. To gain deeper insight into the regulatory role of AtbZIP18, we analysed atbzip18/- pollen microarray data. Our results point towards a potential repressive role for AtbZIP18 and its functional redundancy with AtbZIP34 in pollen.

• Keywords
• Male gametophyte, Pollen development, Regulatory network, Transcription factors, Y2H, bZIP,
• MeSH
• Arabidopsis cytology   metabolism   ultrastructure   MeSH
• Dimerization MeSH
• DNA, Plant MeSH
• Mutagenesis, Insertional MeSH
• Arabidopsis Proteins metabolism   MeSH
• Pollen genetics   growth & development   metabolism   ultrastructure   MeSH
• Gene Expression Regulation, Plant MeSH
• Recombinant Fusion Proteins metabolism   MeSH
• Trans-Activators metabolism   MeSH
• Basic-Leucine Zipper Transcription Factors metabolism   MeSH
• Protein Binding MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• bZIP18 protein, Arabidopsis MeSH Browser
• bZIP34 protein, Arabidopsis MeSH Browser
• DNA, Plant MeSH
• Arabidopsis Proteins MeSH
• Recombinant Fusion Proteins MeSH
• Trans-Activators MeSH
• Basic-Leucine Zipper Transcription Factors MeSH