Multiple transcriptional regulation of walnut JrGSTTau1 gene in response to osmotic stress

The regulation of glutathione s-transferases by gibberellic acid application in salt treated maize leaves

Plant hormones and antioxidant system changes occur during plants' exposure to stress conditions. Although the interactions of some plant hormones (abscisic acid, salicylic acid, jasmonic acid, nitric oxide, and ethylene) with the glutathione s-transferase (GST) enzyme, which is one of the antioxidant enzymes, have already been reported, the influence of gibberellic acid (GA3) on this enzyme under saline conditions has not yet been reported. Plant material for the experiments was obtained from M14G144 cultivar of maize (Zea mays L.) plants grown as a soil culture in growth chambers at 22 °C, 65-70% moisture, 16-h light/8-h dark conditions, and with full strength Hoagland solution for 8 days under controlled growth conditions. Then, the plants were exposed to salt stress (350 mM NaCl and 100, 300, and 500 ppm GA3) simultaneously. In maize leaves, GA3 treatment alleviated the physiological parameters under salt stress. Specifically, the treatments with 100 and 500 ppm of GA3 were able to trigger GST enzyme and isoenzyme activities as well as hydrogen sulfide accumulation and anthocyanin content, although the lowest malondialdehyde, hydrogen peroxide, and superoxide radical content were under the treatment of 300 ppm of GA3. Besides this, GST gene expression levels were found to be upregulated between 1.5 and fourfold higher in all the plants treated with GA3 at different concentrations in proportion to salt stress. These results first indicated that the reason for the changes in GA3-treated plants was the stimulating role of this hormone to maintain GST regulation in maize plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01269-2.

Identifying and expression analysis of WD40 transcription factors in walnut

Walnut (Juglans regia L.) is an important woody oil plant and will be affected by abiotic and biological stress during its growth and development. The WD-repeat (WD40) protein is widely involved in plant growth, development, metabolism, and abiotic stress response. To explore the stress response mechanism of walnut, based on the complete sequencing results of the walnut genome, this study identified and analyzed the physiological, biochemical, genetic structure, and conservative protein motifs of 42 JrWD40 genes, whose expression to abnormal temperature were tested to predict the potential biological function. The results showed that the open reading frame (ORF) of theseWD40 genes were 807-2,460 bp, encoding peptides were 29,610.55-90,387.98 Da covering 268-819 amino acids, as well as 12-112 phosphorylation sites. JrWD40 proteins were highly conserved with four to five WD40 domains and shared certain similarity to WD40 proteins from Arabidopsis thaliana (L.) Heynh. JrWD40 genes can be induced to varying degrees by low and high temperature treatments. JrWD40-32, JrWD40-27, JrWD40-35, and JrWD40-21 are affected by high temperature more seriously and their expression levels are higher; while JrWD40-37, JrWD40-26, JrWD40-20, JrWD40-24, and other genes are inhibited under low temperature stress. JrWD40-40, JrWD40-28, and JrWD40-18 were first suppressed with low expression, while as the treatment time prolonging, the expression level was increased under cold condition. JrWD40-14, JrWD40-18, JrWD40-34, and JrWD40-3 displayed strong transcriptions response to both heat and cold stress. These results indicated that JrWD40 genes can participate in walnut adaptation to adversity and can be used as important candidates for walnut resistance molecular breeding.

Genome-wide identification and expression analysis of ethylene responsive factor family transcription factors in Juglans regia

Background

Walnut is an important economic tree species with prominent economic value and ecological functions. However, in recent years, walnuts have become susceptible to drought stress, resulting in a decline in comprehensive benefits. Therefore, it is necessary to identify the regulatory molecular mechanism associated with walnut response to drought. In many plants, ethylene responsive factor (ERF) gene family plays important roles in response to biotic and abiotic stress, especial drought. Therefore, the identification and characterisation of walnut ERF genes will benefit walnut with regard to the clarification of drought response mechanism as well as the management, production, and quality of plantations.

Methods

‘ERF’ was compared against the walnut transcriptome, and the JrERFs with a complete open reading frame (ORF) were identified by ORF Finder. The molecular weights, amino acid residues, and theoretical isoelectric point (pI) were predicted by ExPASy. The distribution of JrERFs in chromosome locations was determined based on walnut genome data from NCBI. The intron-exon structures and conserved domains were analysed using Gene Structure Display Server 2.0 and CD-Search, accordingly. Multi-sequence alignment and a phylogenetic tree were constructed by ClustalX2.1 and MEGA7, respectively. The conserved motifs were acquired using MEME. Total RNA was isolated using the cetyltrimethylammonium ammonium bromide (CTAB) method (Yang et al., 2018). Gene expression was determined by using real-time quantitative polymerase chain reaction (qRT-PCR) analysis and calculated according to the 2^−ΔΔCT method (Livak & Schmittgen, 2001).

Results

A total of 44 JrERFs were identified from the walnut transcriptome, whose ORFs were 450–1,239 bp in length. The molecular weights of the JrERF proteins (consisting 149–412 amino acids) were 16.81–43.71 kDa, with pI ranging from 4.8 (JrERF11) to 9.89 (JrERF03). The JrERFs can be divided into six groups (B1–B6), and among the groups, B6 contained the most number of members. Each JrERF contained 1–6 motifs and each motif comprised 9–50 amino acids. Among the motifs, motif1, motif2, and motif3 were the most abundant. More than 40% of JrERFs were up-regulated continuously when subjected to ethephon (ETH), PEG₆₀₀₀, and PEG₆₀₀₀+ETH treatments. Of all the JrERFs, JrERF11 showed the highest expression. Therefore, we conclude that walnut ERF genes are highly conserved and involved in the regulation of drought response in the presence of ETH. JrERFs are possibly important candidate genes for molecular breeding; hence, the findings of this study provides the theoretical basis for further investigation of ERF genes in walnut and other species.

Walnut ethylene response factor JrERF2-2 interact with JrWRKY7 to regulate the GSTs in plant drought tolerance

Juglans regia is a world-famous woody oil plant, whose yield and quality are affected by drought stress. Ethylene-responsive factors (ERFs) play vital role in plant stress response. In current study, to comprehend the walnut molecular mechanism of drought stress response, an ERF transcription factor was clarified from J. regia (JrERF2-2) and its potential function mechanism to drought was clarified. The results showed that JrERF2-2 could be induced significantly by drought. The transgenic Arabidopsis over-expression of JrERF2-2 displayed enhanced growth, antioxidant enzyme vitalities, reactive oxygen species scavenging and proline produce under drought stress. Especial the glutathione-S-transferase (GST) activity and most GST genes' transcription were elevated obviously. Yeast one-hybrid (Y1H) and co-transient expression (CTE) methods revealed that JrERF2-2 could recognize JrGST4, JrGST6, JrGST7, JrGST8, and JrGSTF8 by binding to GCC-box, and recognize JrGST11, JrGST12, and JrGSTN2 by binding to DRE motif. Meanwhile, the binding activity was strengthened by drought stress. Moreover, JrERF2-2 could interact with JrWRKY7 to promote plant drought tolerance; JrWRKY7 could also distinguish JrGST4, JrGST7, JrGST8, JrGST11, JrGST12, and JrGSTF8 via binding to W-Box motif. These results suggested that JrERF2-2 could effectively improve plant drought tolerance through interacting with JrWRKY7 to control the expression of GSTs. JrERF2-2 is a useful plant representative gene for drought response in molecular breeding.

Identification of Glutathione S-Transferase Genes in Hami Melon (Cucumis melo var. saccharinus) and Their Expression Analysis Under Cold Stress

As a group of multifunctional enzymes, glutathione S-transferases (GSTs) participate in oxidative stress resistance and cellular detoxification. Here, we identified 39 CmGST genes with typical binding sites from the Hami melon genome, and they can be classified into seven subfamilies. Their molecular information, chromosomal locations, phylogenetic relationships, synteny relationships, gene structures, protein-protein interactions, structure of 3-D models, and expression levels under cold stress were analyzed. Expression analysis indicates that cold-tolerant Jia Shi-310 (JS) had higher GST enzyme activities and expression levels of 28 stress-related genes under cold stress. Some CmGSTs belonging to Tau, Phi, and DHAR classes play significant roles under cold stress, and they could be regarded as candidate genes for further studies. The present study systematically investigated the characterization of the Hami melon GST gene family, extending our understanding of Hami melon GST mediated stress-response mechanisms in this worldwide fruit.