Ethylene plays an important role in plant development and stress resistance. The rate-limiting enzyme in ethylene biosynthesis is 1-aminocyclopropane-1-carboxylic acid synthase (ACS). C. quinoa (Chenopodium quinoa) is an important food crop known for its strong tolerance to abiotic stresses. However, knowledge regarding the ACS gene family in C. quinoa remains restricted. In this study, we successfully identified 12 ACS genes (CqACSs) from the C. quinoa genome. Through thorough analysis of their sequences and phylogenetic relationships, it was verified that 8 out of these 12 CqACS isozymes exhibited substantial resemblance to ACS isozymes possessing ACS activity. Furthermore, these eight isozymes could be categorized into three distinct groups. The four remaining CqACS genes grouped under category IV displayed notable similarities with AtACS10 and AtACS12, known as amido transferases lacking ACS activity. The CqACS proteins bore resemblance to the AtACS proteins and had the characteristic structural features typically observed in plant ACS enzymes. Twelve CqACS genes were distributed across 8 out of the 18 chromosomes of C. quinoa. The CqACS genes were expanded from segment duplication. Many cis-regulatory elements related with various abiotic stresses, phytohormones, and light were found. The expression patterns of ACS genes varied across different tissues of C. quinoa. Furthermore, the analysis of gene expression patterns under abiotic stress showed that CqACS genes can be responsive to various stresses, implying their potential functions in adapting to various abiotic stresses. The findings from this research serve as a foundation for delving deeper into the functional roles of CqACS genes.

Plant protein phosphatase 2Cs (PP2Cs) function as inhibitors in protein kinase cascades involved in various processes and are crucial participants in both plant development and signaling pathways activated by abiotic stress. In this study, a genome-wide study was conducted on the CqPP2C gene family. A total of putative 117 CqPP2C genes were identified. Comprehensive analyses of physicochemical properties, chromosome localization and subcellular localization were conducted. According to phylogenetic analysis, CqPP2Cs were divided into 13 subfamilies. CqPP2Cs in the same subfamily had similar gene structures, and conserved motifs and all the CqPP2C proteins had the type 2C phosphatase domains. The expansion of CqPP2Cs through gene duplication was primarily driven by segmental duplication, and all duplicated CqPP2Cs underwent evolutionary changes guided by purifying selection. The expression of CqPP2Cs in various tissues under different abiotic stresses was analyzed using RNA-seq data. The findings indicated that CqPP2C genes played a role in regulating both the developmental processes and stress responses of quinoa. Real-time quantitative reverse transcription PCR (qRT-PCR) analysis of six CqPP2C genes in subfamily A revealed that they were up-regulated or down-regulated under salt and drought treatments. Furthermore, the results of yeast two-hybrid assays revealed that subfamily A CqPP2Cs interacted not only with subclass III CqSnRK2s but also with subclass II CqSnRK2s. Subfamily A CqPP2Cs could interact with CqSnRK2s in different combinations and intensities in a variety of biological processes and biological threats. Overall, our results will be useful for understanding the functions of CqPP2C in regulating ABA signals and responding to abiotic stress.

Plant protein phosphatase 2Cs (PP2Cs) serve as negative regulators of protein kinase cascades activated in different processes and play important roles in plant development and abiotic-stress-mediated signaling pathways. In this study, a genome-wide study was conducted on the CqPP2C gene family. A total of putative 117 CqPP2C genes were identified. Comprehensive analyses of physical and chemical feature, chromosome localization and subcellular localization were conducted. According to phylogenetic analysis, CqPP2Cs were divided into 13 subfamilies. CqPP2Cs in the same subfamily had similar gene structure, conserved motif and all the CqPP2C proteins had the type 2C phosphatase domains. Gene duplication revealed that segmental duplication was the major driving force for CqPP2Cs expansion and all duplicated CqPP2Cs evolved from purifying selection. The expression of CqPP2Cs in various tissues under different abiotic stresses was analyzed using RNA-seq data. The results revealed that CqPP2C genes were involved in regulating development and stress responses of quinoa. Real-time quantitative reverse transcription PCR (qRT-PCR) analysis of six CqPP2C genes in subfamily A revealed that they were up-regulated or down-regulated under salt and drought treatments. Furthermore, the results of yeast two-hybrid assays revealed that subfamily A CqPP2Cs interacted not only with subclass III CqSnRK2s, but also with subclass II CqSnRK2s. Subfamily A CqPP2Cs could interact with CqSnRK2s in different combinations and intensities to respond to various biological processes and stresses. Overall, our results will be useful for understanding the functions of CqPP2C in regulating ABA signals and responding to abiotic stress.

Heat shock protein 90 (HSP90) is an evolutionarily conserved molecular chaperone. Numerous studies have shown that it is widely involved in protein folding, assembly, stabilization, activation, and degradation in response to various biotic and abiotic stresses in many normal cellular processes and under stress conditions. We identified 11 members of the CqHSP90 gene family in the quinoa (Chenopodium quinoa) genome by bioinformatics analysis. Phylogenetic tree analysis showed that quinoa was more closely related to dicotyledonous plants than to monocotyledonous plants. Quinoa is susceptible to high-temperature stress during its growth and development. We analyzed the cis-acting elements of its promoter, and found that nearly 1/3 of the cis-acting elements were stress-responsive, and 2/3 of them had heat-responsive elements. The results of qRT-PCR showed that heat shock at 40 °C could induce a high expression of CqHSP90.1c and CqHSP90.6a. Subcellular localization indicates that they are all membrane proteins. At the same time, both CqHSP90.1c and CqHSP90.6a overexpression lines improved the tolerance of Arabidopsis thaliana under high temperature, indicating that both of them had a positive regulatory effect under heat stress. Results of this study could provide useful information for further study on the biological role of CqHSP90.1c and CqHSP90.6a, and provide theoretical basis for quinoa resistance breeding.

Glutathione peroxidase (GPX) is crucial in mediating plant responses to abiotic stresses. In this study, bioinformatics methods were used to identify the GPX gene family in quinoa. A total of 15 CqGPX genes were identified at the quinoa genome level and conducted preliminary analysis on their protein characteristics, chromosome distribution, gene structure, conserved domain structure, cis-acting elements, and expression patterns. Phylogenetic analysis showed that the GPX genes of quinoa, Arabidopsis, soybean, rice, and maize were divided into three groups. Most of the CqGPXs had the three characteristic conserved motifs and other conserved sequences and amino acid residues. Six types of cis-acting elements were identified in the CqGPX gene promoter, with stress and hormone response-related cis-acting elements constituting the two main categories. Additionally, the expression patterns of CqGPX genes across various tissues and their responses to treatments with NaCl, PEG, CdCl₂, and H₂O₂ were also investigated. The qRT-PCR results showed significant differences in the expression levels of the CqGPX genes under stress treatment at different time points. Consistently, the activity of glutathione peroxidase enzymes increased under stresses. Heterologous expression of CqGPX4 and CqGPX15 conferred stress tolerance to E. coli. This study will provide a reference for exploring the function of CqGPX genes.

Quinoa is a high-nutrition crop originating from the Andes Mountains that is tolerant to cold, drought and salt. However, the mechanism of the high-temperature response in quinoa is still unclear. In this study, quinoa line YL-6 was used to analyze the changes in photosynthetic parameters, physiological parameters and the transcriptome after 0, 3, 12 and 24 h of heat stress. Our results showed that photosynthetic parameters, including the maximum quantum yield of PSII (Fv/Fm), steady-state effective quantum yield (ΦPSII_Lss), non-photochemical quenching (NPQ_Lss), and photochemical quenching coefficients (qL_Lss, qP_Lss), decreased significantly under heat stress, whereas the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), increased significantly at the early stage. The contents of osmotic adjustment substances such as proline, soluble protein and soluble sugar showed a non-single change trend. WGCNA was conducted to group the differentially expressed genes (DEGs) into 12 co-expression modules. Key modules associated with heat perception and signal transduction were identified, and a core regulatory network was subsequently constructed. Hub genes encoding molecular chaperones and transcription factors were screened, among which heat shock proteins (HSPs) were the most prominent. These results could provide a theoretical basis for analyzing the regulatory network of heat stress, exploring heat-resistant genes and introducing and domesticating quinoa.