In order to clarify the effects of drought stress training on the quality and drought resistance of Codonopsis pilosula, this study used PEG to simulate drought stress and employed potting with water control for the drought stress training of C. pilosula plants. The polysaccharide content, secondary metabolites, antioxidant system, and photosynthetic pigment system of C. pilosula after drought stress training were analyzed. The results showed that the content of fructans in the root of C. pilosula increased after two rounds of drought stress treatment, and it was significantly higher than that of the control group. The accumulation of fructans in the root of C. pilosula showed an upward trend during the rehydration treatment. The content of lobetyolin and tangshenoside Ⅰ increased after drought stress treatment compared with that of the control group. The rehydration treatment caused first increasing and then decreasing in the content of lobetyolin, while it had no significant effect on the tangshenoside Ⅰcontent. The content of photosynthetic pigments decreased after drought stress treatment, and it gradually increased during the first round of rehydration and the second round of rehydration. Moreover, the increase was faster in the second round of rehydration than in the first round of rehydration. The content of the peroxidation product malondialdehyde(MDA) and the activities of superoxide dismutase(SOD), peroxidase(POD), and catalase(CAT) increased after drought stress treatment compared with those of the control group, and they showed a tendency of decreasing during rehydration. Moreover, the decrease was faster in the second round of rehydration than in the first round of rehydration. When the plants of C. pilosula after drought stress training were again subjected to severe drought stress, the wilting rate decreased significantly, and the biomass increases significantly. This study showed that the drought stress training could promote the accumulation of polysaccharides and secondary metabolites in the root of C. pilosula. When encountering drought stress again, C. pilosula plants could quickly regulate the antioxidant system and delay the decomposition of chlorophyll to respond to drought stress. The findings provide a theoretical basis for the ecological cultivation of C. pilosula in arid and semi-arid areas.
Codonopsis/growth & development* ; Droughts ; Polysaccharides/metabolism* ; Stress, Physiological ; Water/metabolism* ; Antioxidants/metabolism* ; Photosynthesis ; Drought Resistance

Autophagy is an evolutionarily conserved self-degradation process in eukaryotes. It not only plays a role in plant growth and development but also is involved in plant responses to biotic and abiotic stresses. Plants can initiate autophagy to degrade the surplus or damaged cytoplasmic materials and organelles, thus coping with abiotic and biotic stresses. The initiation of autophagy depends on autophagy-related genes (ATGs). The transcription factors can directly bind to the promoters of ATGs to activate autophagy and regulate their transcriptional levels and post-translational modifications. Furthermore, ATGs can directly or indirectly interact with plant hormones to regulate plant responses to stresses. When plants are exposed to salinity, drought, extreme temperatures, nutrient deficiencies, and pathogen stress, ATGs are significantly induced, which enhances the autophagy activity to facilitate the degradation of the denatured and misfolded proteins, thereby enhancing plant tolerance to adversity stresses. This article summarizes the discovery, structures, and classification of plant ATGs, reviews the research progress in the mechanisms of ATGs in plant responses to abiotic and biotic stresses, and prospects the future research directions. This review is expected to provide the genetic resources and a theoretical foundation for the genetic improvement of crops in responses to stress tolerance.
Autophagy/physiology* ; Stress, Physiological/genetics* ; Gene Expression Regulation, Plant ; Plants/metabolism* ; Transcription Factors/metabolism* ; Plant Proteins/genetics* ; Genes, Plant ; Plant Physiological Phenomena ; Droughts

Prunus mume is an ecologically and economically valuable plant with both medicinal and edible values. However, drought severely limits the promotion and cultivation of P. mume in the arid and semi-arid areas in northern China. In this study, we treated P. mume 'Meiren' with natural drought and then assessed photosynthetic and physiological indexes such as osmoregulatory substances, photosynthetic parameters, and antioxidant enzyme activities. Furthermore, we employed transcriptome sequencing to explore the internal regulatory mechanism of P. mume under drought stress. As the drought stress aggravated, the levels of chlorophyll a (Chla), chlorophyll b (Chlb), chlorophyll (a+b)[Chl(a+b)], and soluble protein (SP) in P. mume first elevated and then declined. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum photochemical efficiency (Fv/Fm), effective photochemical quantum yield [Y(Ⅱ)], photochemical quenching (qP), and relative electron transport rate (ETR) all kept decreasing, while the levels of malondialdehyde, superoxide dismutase (SOD), peroxidase (POD), and osmoregulatory substances rose. Transcriptome sequencing revealed a total of 24 853 high-quality genes. Gene ontology (GO) enrichment showed that differentially expressed genes (DEGs) were the most under severe drought. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis showed that the DEGs during the four drought periods were mainly involved in the biosynthesis of secondary metabolites, plant-pathogen interaction, plant hormone signal transduction, starch and sucrose metabolism, and mitogen-activated protein kinase signaling pathways. Furthermore, we identified 16 key genes associated with the drought tolerance of P. mume 'Meiren'. This study discovered that P. mume might up-regulate or down-regulate the expression of drought tolerance-related genes such as SUS, P5CS, LEA, SOD, POD, SOD1, TPPD, and TPPA via transcription factors like MYB, ERF, bHLH, NAC, and WRKY to promote the accumulation of osmoregulatory substances like sucrose and enhance the activities of antioxidant enzymes such as SOD and POD, thus reducing the harm of reactive oxygen species and protecting the structure and function of the membrane system under drought stress. The findings provide theoretical references for further exploration of candidate genes of P. mume in response to drought stress and breeding of drought-tolerant varieties.
Droughts ; Photosynthesis/physiology* ; Gene Expression Regulation, Plant ; Stress, Physiological/genetics* ; Prunus/genetics* ; Chlorophyll/metabolism* ; Plant Proteins/genetics*

The plant AT-rich sequence and zinc-binding protein (PLATZ) family is composed of plant-specific zinc finger-like transcription factors, which play important roles in plant growth, development, and stress tolerance. In this study, to gain a better understanding of the PLATZ gene in C. sinensis and elucidate its response under drought and high temperature conditions, the PLATZ gene family of the C. sinensis cultivar 'Tieguanyin' was systematically identified, and a total of 12 CsPLATZ family members were identified. Expasy online and other bioinformatics tools were used to analyze the members of the PLATZ gene family in terms of protein physicochemical properties, phylogenetic relationships, cis-acting elements, gene structures, and intra- and inter-species collinearity. The results of phylogenetic analysis classified the CsPLATZ family members into 2 subfamilies. The conserved domains and gene structures of PLATZ family members within the same subfamily had a high degree of consistency, whereas a certain degree of diversity was observed among the subfamilies. Twelve PLATZ genes were unevenly distributed across 7 chromosomes of C. sinensis and the promoter regions of these genes had multiple cis-acting elements related to hormone and stress responses. The collinearity analysis showed that there were 4 pairs of duplication events in the CsPLATZ gene family, all of which were segmental duplications. Based on this gene family, C. sinensis had a closer evolutionary relationship with A. thaliana than with O. sativa. The transcriptome analysis showed that the expression levels of CsPLATZ family members varied in different tissue samples of C. sinensis. 6 genes (CsPLATZ-1, CsPLATZ-2, CsPLATZ-3, CsPLATZ-4, CsPLATZ-6, and CsPLATZ-8) with high expression in shoots, young leaves, and roots were selected for high temperature and drought stress treatments, and their expression was quantified by qRT-PCR. The results indicated that the six genes might play important roles in the response to drought stress. In addition, CsPLATZ-2 and CsPLATZ-8 might have important functions in the response to high temperature stress. The results of this study will contribute to a better understanding of the biological functions of PLATZ genes and their possible roles in the growth, development, and stress responses of C. sinensis.
Droughts ; Camellia sinensis/physiology* ; Phylogeny ; Gene Expression Regulation, Plant ; Plant Proteins/genetics* ; Stress, Physiological/genetics* ; Multigene Family ; Transcription Factors/genetics* ; Hot Temperature ; Genes, Plant

To explore the regulatory mechanism of drought stress on the synthesis of chlorogenic acid and luteoloside in Lonicera japonica, we designed five drought gradients (soil water contents of 30%, 24%, 17%, 14%, and 10%) and screened and verified the differentially expressed genes (DEGs) by RNA sequencing (RNA-seq) and reverse transcription quantitative polymerase chain reaction (RT-qPCR). Furthermore, we employed HPLC to systematically measure the content changes of chlorogenic acid and luteoloside. The results revealed that drought significantly reduced the accumulation of secondary metabolites, and severe drought led to more obvious reductions. Under extreme drought (soil water content of 10%), the content of chlorogenic acid and luteoloside decreased significantly to 25.73 mg/g and 11.33 mg/g (with the decrease rates of 37.85% and 9.58%, respectively). A total of 77 454 genes were identified via transcriptome analysis, among which the number of DEGs reached 1 128 under the extraordinary drought. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses revealed that the DEGs were mainly involved in flavonoid synthesis, secondary metabolite biosynthesis, plant hormone signal transduction and the plant-pathogen interaction pathways, and the expression of key genes regulating the synthesis of chlorogenic acid and luteoloside was significantly downregulated. RT-qPCR verified the accuracy of the RNA-seq data. This study revealed that drought stress reduced the content of chlorogenic acid and luteoloside, the main secondary metabolites, by inhibiting the expression of key genes in the secondary metabolism pathways. The findings provide candidate gene resources for molecular breeding of drought-tolerant Lonicera japonica.
Lonicera/physiology* ; Chlorogenic Acid/metabolism* ; Droughts ; Stress, Physiological ; Gene Expression Regulation, Plant ; Glucosides/metabolism* ; Luteolin

WRKYs is a unique family of transcription factors (TFs) in plants, and belongs to the typical multifunctional regulator. It is involved in the regulation of multiple signaling pathways. This type of transcription factor is characterized to contain about 60 highly conservative amino acids as the WRKY domain, and usually also has the Cys2His2 or Cys2His-Cys zinc finger structure. WRKYs can directly bind to the W-box sequence ((T)(T) TGAC (C/T)) in the promoter region of the downstream target gene, and activate or inhibit the transcription of the target genes by interacting with the target protein. They may up-regulate the expression of stress-related genes through integrating signal pathways mediated by abscisic acid (ABA) and reactive oxygen species (ROS), thus playing a vital role in regulating plant response to abiotic stresses. This review summarizes the advances in research on the structure and classification, regulatory approach of WRKYs, and the molecular mechanisms of WRKYs involved in response to drought and salt stresses, and prospects future research directions, with the aim to provide a theoretical support for the genetic improvement of crop in response to abiotic stresses.
Transcription Factors/genetics* ; Abscisic Acid ; Amino Acids ; Droughts ; Stress, Physiological/genetics*

To explore the changes and the reaction mechanisms between soil microecological environment and the content of secon-dary metabolites of plants under water deficit, this study carried out a pot experiment on the 3-leaf stage seedlings of Rheum officinale to analyze their response mechanism under different drought gradients(normal water supply, mild, moderate, and severe drought). The results indicated that the content of flavonoids, phenols, terpenoids, and alkaloids in the root of R. officinale varied greatly under drought stresses. Under mild drought stress, the content of substances mentioned above was comparatively high, and the content of rutin, emodin, gallic acid, and(+)-catechin hydrate in the root significantly increased. The content of rutin, emodin, and gallic acid under severe drought stress was significantly lower than that under normal water supply. The number of species, Shannon diversity index, richness index, and Simpson index of bacteria in the rhizosphere soil were significantly higher than those in blank soil, and the number of microbial species and richness index decreased significantly with the aggravation of drought stresses. In the context of water deficit, Cyanophyta, Firmicutes, Actinobacteria, Chloroflexi, Gemmatimonadetes, Streptomyces, and Actinomyces were the dominant bacteria in the rhizosphere of R. officinale. The relative content of rutin and emodin in the root of R. officinale was positively correlated with the relative abundance of Cyanophyta and Firmicutes, and the relative content of(+)-catechin hydrate and(-)-epicatechin gallate was positively correlated with the relative abundance of Bacteroidetes and Firmicutes. In conclusion, appropriate drought stress can increase the content of secondary metabolites of R. officinale from physiological induction and the increase in the association with beneficial microbe.
Rhizosphere ; Rheum ; Droughts ; Soil ; Catechin ; Emodin ; Bacteria/metabolism* ; Water/metabolism* ; Firmicutes ; Soil Microbiology

Galactinol synthase (GolS) genes play important roles in plant response to abiotic stress. In this research, the plant expression vector of soybean GmGolS2-2 gene was constructed and transformed into tobacco to study the drought tolerance of transgenic tobacco. A GmGolS2-2 gene with 975 bp coding sequence was cloned from soybean leaves by reverse transcription-polymerase chain reaction (RT-PCR). GmGolS2-2 was linked to the plant expression vector pRI101 by restriction enzyme sites Nde Ⅰ and EcoR Ⅰ, and transformed into tobacco by leaf disc method. Genomic DNA PCR and real-time PCR showed that three GmGolS2-2 transgenic tobacco plants were obtained. The growth status of GmGolS2-2 transgenic tobacco under drought stress was better than that of wild-type tobacco. After drought stress treatment, the electrolyte leakage and malondialdehyde content of transgenic tobacco were lower than those of wild-type tobacco, but the proline content and soluble sugar content were higher than those of wild-type tobacco. The results of real-time PCR showed that the heterologous expression of GmGolS2-2 increased the expression of stress-related genes NtERD10C and NtAQP1 in transgenic tobacco. The above results indicated that GmGolS2-2 improved drought resistance of transgenic tobacco.
Drought Resistance ; Tobacco/genetics* ; Soybeans/genetics* ; Plant Proteins/metabolism* ; Plants, Genetically Modified/genetics* ; Stress, Physiological/genetics* ; Droughts ; Gene Expression Regulation, Plant

The NAC(NAM/ATAF/CUC) transcription factors are members of the largest transcriptional gene family in plants and play an essential role in the response of plants to drought stress. To identify the number and function of the NAC gene family in Carthamus tinctorius, the present study adopted bioinformatics methods to identify NAC gene family members based on the whole genome data of C. tinctorius, and analyzed their physicochemical properties, chromosomal location, phylogenetic relationship, gene structure, conserved domain, and conserved motif. Meanwhile, the real-time fluorescence-based quantitative RT-PCR(qRT-PCR) was used to analyze the transcription level of four NAC genes under drought stress in different time. The results showed that C. tinctorius contained 87 NAC genes unevenly distributed on 11 chromosomes, while no NAC gene was found on chromosome 12. The encoded proteins were 103-974 amino acids and the number of CDS ranged from 3 to 9. According to the phylogenetic relationships, 87 NAC genes were clustered into17 subfamilies. The analysis of conserved domains and motifs revealed that most of the genes contained five conserved subdomains, A-E and motif2 was the most conserved among NAC genes. The expression pattern analysis showed that the transcription levels of four NAC genes related to drought resistance were all up-regulated after drought stress treatment for different time, suggesting that these four NAC genes may be related to drought resistance of C. tinctorius. This study is expected to provide a theoretical basis for further functional analysis of NAC transcription factors in C. tinctorius and references for the cultivation of drought-tolerant C. tinctorius varieties.
Droughts ; Carthamus tinctorius/genetics* ; Gene Expression Regulation, Plant ; Plant Proteins/metabolism* ; Phylogeny ; Transcription Factors/metabolism* ; Stress, Physiological/genetics* ; Multigene Family

Galactinol synthase (GolS) is a key enzyme in the biosynthetic pathway of raffinose family oligosaccharides (RFOs) and plays an important role in plant responses to abiotic stresses. However, the molecular characteristics of the GolS family members in soybean was not well-known. In this study, six members of GmGolS gene family were genome-widely identified, and their physicochemical properties, chromosomal localization, evolutionary relationship, gene structure, conserved motifs, secondary structure, tertiary structure, tissue-specific expression patterns and the expression levels under salt and drought stresses were analyzed. The results showed that six soybean GolS genes were unevenly distributed on four chromosomes, the range of the isoelectric points of six GmGolS proteins was 5.45-6.08, the molecular weight range was 37 567.07-38 817.59 Da, and the number of amino acids was 324-339 aa. The results of subcellular localization showed that 4 proteins were located in the chloroplast, and 2 proteins in the cytoplasm. Phylogenetic tree analysis showed that the members of the soybean GolS gene family were closely adjacent to each other, and were evolutionarily conservative. Six gene members contain 3 or 4 exons. Prediction of secondary and tertiary structures showed that the spatial structure of proteins of all family members was mainly composed of α-helix and random coil structure, with less β-turn and extended chain structure. Tissue-specific expression analysis showed that six GmGolS members expressed to variable degrees in seeds, roots, root hairs, flowers, stems, pods, nodules and leaves. Expression analysis based on qRT-PCR showed that all GmGolS genes showed different degrees of up-regulated expression under salt and drought treatment, indicating that these genes may be related to the response of plants to salt-tolerance and drought-resistance. These results may facilitate subsequent functional analysis of soybean GolS genes.
Droughts ; Soybeans/genetics* ; Phylogeny ; Plant Proteins/metabolism* ; Stress, Physiological/genetics* ; Plants/metabolism* ; Gene Expression Regulation, Plant