A bZIP transcription factor accelerates the transition to reproductive tuber growth and aging in Solanum tuberosum

TCP transcription factor StAST1 represses potato tuberization by regulating tuberigen complex activity

Potato (Solanum tuberosum L.) is cultivated worldwide for its underground tubers, which provide an important part of human nutrition and serve as a model system for belowground storage organ formation. Similar to flowering, stolon-expressed FLOWERING LOCUS T-like (FT-like) protein SELF-PRUNING 6A (StSP6A) plays an instrumental role in tuberization by binding to the bZIP transcription factors StABI5-like 1 (StABL1) and StFD-like 1 (StFDL1), causing transcriptional reprogramming at the stolon subapical apices. However, the molecular mechanism regulating the widely conserved FT-bZIP interactions remains largely unexplored. Here, we identified a TCP transcription factor StAST1 (StABL1 and StSP6A-associated TCP protein 1) binding to both StSP6A and StABL1. StAST1 is specifically expressed in the vascular tissue of leaves and developing stolons. Silencing of StAST1 leads to accelerated tuberization and a shortened life cycle. Molecular dissection reveals that the interaction of StAST1 with StSP6A and StABL1 attenuates the formation of the alternative tuberigen activation complex (aTAC). We also observed StAST1 directly activates the expression of potato GA 20-oxidase gene (StGA20ox1) to regulate GA responses. These results demonstrate StAST1 functions as a tuberization repressor by regulating plant hormone levels; our findings also suggest a mechanism by which the widely conserved FT-FD genetic module is fine-tuned.

Cucumis sativus CsbZIP90 suppresses Podosphaera xanthii resistance by modulating reactive oxygen species

Resistance to disease in plants requires the coordinated action of multiple functionally related genes, as it is difficult to improve disease resistance with a single functional gene. Therefore, the use of transcription factors to regulate the expression of multiple resistance genes to improve disease resistance has become a recent focus in the field of gene research. The basic leucine zipper (bZIP) transcription factor family plays vital regulatory roles in processes, such as plant growth and development and the stress response. In our previous study, CsbZIP90 (Cucsa.134370) was involved in the defense response of cucumber to Podosphaera xanthii, but the relationship between cucumber and resistance to powdery mildew remained unclear. Herein, we detected the function of CsbZIP90 in response to P. xanthii. CsbZIP90 was localized to the cytoplasm and nucleus, and its expression was significantly induced during P. xanthii attack. Transient overexpression of CsbZIP90 in cucumber cotyledons resulted in decreased resistance to P. xanthii, while silencing CsbZIP90 increased resistance to P. xanthii. CsbZIP90 negatively regulated the expression of reactive oxygen species (ROS)-related genes and activities of ROS-related kinases. Taken together, our results show that CsbZIP90 suppresses P. xanthi resistance by modulating ROS. This study will provide target genes for breeding cucumbers resistant to P. xanthii.

bZIP transcription factor FabR: Redox-dependent mechanism controlling docosahexaenoic acid biosynthesis and H2O2 stress response in Schizochytrium sp

Schizochytrium sp. is an important industrial strain for commercial production of docosahexaenoic acid (DHA), which plays essential physiological roles in infant development and human health. The regulatory network for DHA biosynthesis and lipid accumulation in Schizochytrium remains poorly understood. FabR (fatty acid biosynthesis repressor), a basic leucine zipper (bZIP) transcription factor, was transcriptionally downregulated under low-nitrogen condition. Deletion of fabR gene (mutant ΔfabR) increased production of total lipids and DHA by 30.1% and 46.5%, respectively. ΔfabR displayed H2O2 stress resistance higher than that of parental strain or complementation strain CfabR. FabR bound specifically to 7-bp pseudo-palindromic sequence 5'-ATTSAAT-3' in upstream regions and repressed transcription of fatty acid biosynthesis genes (acl, fas, pfa) and antioxidant defense genes (cat, sod1, sod2, gpx). DNA binding activity of FabR was regulated in a redox-dependent manner. Under oxidative condition, FabR forms intermolecular disulfide bonds between two Cys46 residues of dimers; its DNA binding activity is thereby lost, and the transcription of its target genes is enhanced through derepression. Our findings clarify the redox-dependent mechanism that modulates FabR activity governing lipid and DHA biosynthesis and H2O2 stress response in Schizochytrium.

Role of bZIP Transcription Factors in Response to NaCl Stress in Tamarix ramosissima under Exogenous Potassium (K+)

Salt stress is a significant environmental factor affecting plant growth and development, with NaCl stress being one of the most common types of salt stress. The halophyte, Tamarix ramosissima Ledeb (T. ramosissima), is frequently utilized for the afforestation of saline-alkali soils. Indeed, there has been limited research and reports by experts and scholars on the regulatory mechanisms of basic leucine zipper (bZIP) genes in T. ramosissima when treated with exogenous potassium (K+) to alleviate the effects of NaCl stress. This study focused on the bZIP genes in T. ramosissima roots under NaCl stress with additional KCl applied. We identified key candidate genes and metabolic pathways related to bZIP and validated them through quantitative real-time PCR (qRT-PCR). The results revealed that under NaCl stress with additional KCl applied treatments at 0 h, 48 h, and 168 h, based on Pfam protein domain prediction and physicochemical property analysis, we identified 20 related bZIP genes. Notably, four bZIP genes (bZIP_2, bZIP_6, bZIP_16, and bZIP_18) were labeled with the plant hormone signal transduction pathway, showing a predominant up-regulation in expression levels. The results suggest that these genes may mediate multiple physiological pathways under NaCl stress with additional KCl applied at 48 h and 168 h, enhancing signal transduction, reducing the accumulation of ROS, and decreasing oxidative damage, thereby enhancing the tolerance of T. ramosissima to NaCl stress. This study provides gene resources and a theoretical basis for further breeding of salt-tolerant Tamarix species and the involvement of bZIP transcription factors in mitigating NaCl toxicity.