The role of walnut bZIP genes in explant browning

Basic leucine zipper (bZIP) proteins are important transcription factors in plants. To study the role of bZIP transcription factors in walnut explant browning, this study used bioinformatics software to analyze walnut bZIP gene family members, along with their transcript levels in different walnut tissues, to evaluate the transcriptional expression of this gene family during the primary culture of walnut explants and to reveal the mechanism of action of walnut bZIP genes in walnut explant browning.

The results identified 65 JrbZIP genes in the walnut genome, which were divided into 8 subfamilies and distributed on 16 chromosomes. The results of transcriptome data analysis showed that there were significant differences in the expression of four genes, namely, JrbZIP55, JrbZIP70, JrbZIP72, and JrbZIP88, under both vermiculite and agar culture conditions. There were multiple hormone (salicylic acid, abscisic acid, auxin, and gibberellin) signaling and regulatory elements that are responsive to stress (low temperature, stress, and defense) located in the promoter regions of JrbZIP55, JrbZIP70, JrbZIP72, and JrbZIP88. The walnut JrbZIP55 protein and Arabidopsis bZIP42 protein are highly homologous, and the proteins interacting with Arabidopsis bZIP42 include the AT2G19940 oxidoreductases, which act on aldehyde or oxygen-containing donors.

It is speculated that JrbZIP55 may participate in the regulation of browning in walnut explants.