Pengyu Zhang

Nitrogen is one of the important factors restricting the development of sesame planting and industry in China. Cultivating sesame varieties tolerant to low nitrogen is an effective way to solve the problem of crop nitrogen deficiency. To date, the mechanism of low nitrogen tolerance in sesame has not been elucidated at the transcriptional level. In this study, two sesame varieties Zhengzhi HL05 (ZZ, nitrogen efficient) and Burmese prolific (MD, nitrogen inefficient) in low nitrogen were used for RNA-sequencing. A total of 3964 DEGs (differentially expressed genes) and 221 DELs (differentially expressed lncRNAs) were identified in two sesame varieties at 3d and 9d after low nitrogen stress. Among them, 1227 genes related to low nitrogen tolerance are mainly located in amino acid metabolism, starch and sucrose metabolism and secondary metabolism, and participate in the process of transporter activity and antioxidant activity. In addition, a total of 209 pairs of lncRNA-mRNA were detected, including 21 pairs of trans and 188 cis. WGCNA (weighted gene co-expression network analysis) analysis divided the obtained genes into 29 modules; phenotypic association analysis identified three low-nitrogen response modules; through lncRNA-mRNA co-expression network, a number of hub genes and cis/trans-regulatory factors were identified in response to low-nitrogen stress including GS1-2 (glutamine synthetase 1–2), PAL (phenylalanine ammonia-lyase), CHS (chalcone synthase, CHS), CAB21 (chlorophyll a-b binding protein 21) and transcription factors MYB54, MYB88 and NAC75 and so on. As a trans regulator, lncRNA MSTRG.13854.1 affects the expression of some genes related to low nitrogen response by regulating the expression of MYB54, thus responding to low nitrogen stress. Our research is the first to provide a more comprehensive understanding of DEGs involved in the low nitrogen stress of sesame at the transcriptome level. These results may reveal insights into the molecular mechanisms of low nitrogen tolerance in sesame and provide diverse genetic resources involved in low nitrogen tolerance research.

Drought severely affects the growth and development of maize, but there is a certain degree of compensation effect after rewatering. This study intends to elaborate the response mechanism of maize at the physiological and molecular level as well as excavating potential genes with strong drought resistance and recovery ability. Physiological indexes analysis demonstrated that stomata conductance, transpiration rate, photosynthesis rate, antioxidant enzymes, and proline levels in maize were significantly altered in response to drought for 60 and 96 h and rewatering for 3 days. At 60 h, 96 h, and R3d, we detected 3095, 1941, and 5966 differentially expressed genes (DEGs) and 221, 226, and 215 differentially expressed miRNAs. Weighted correlation network analysis (WGCNA) showed that DEGs responded to maize drought and rewatering through participating in photosynthesis, proline metabolism, ABA signaling, and oxidative stress. Joint analysis of DEGs, miRNA, and target genes showed that zma-miR529, miR5072, zma-miR167e, zma-miR167f, zma-miR167j, miR397, and miR6214 were involved to regulate SBPs, MYBs, ARFs, laccases, and antioxidant enzymes, respectively. Hundreds of differentially expressed DNA methylation-related 24-nt siRNA clusters overlap with DEGs, indicating that DNA methylation is involved in responses under drought stress. These results provide new insights into the molecular mechanisms of drought tolerance, and may identify new targets for breeding drought-tolerant maize lines.

OSCAs are hyperosmolality-gated calcium-permeable channel proteins. In this study, two co-expression modules, which are strongly associated with maize proline content, were screened by weighted correlation network analysis, including three ZmOSCA family members. Phylogenetic and protein domain analyses revealed that 12 ZmOSCA members were classified into four classes, which all contained DUF221 domain. The promoter region contained multiple core elements responsive to abiotic stresses and hormones. Colinear analysis revealed that ZmOSCAs had diversified prior to maize divergence. Most ZmOSCAs responded positively to ABA, PEG, and NaCl treatments. ZmOSCA2.3 and ZmOSCA2.4 were up-regulated by more than 200-fold under the three stresses, and showed significant positive correlations with proline content. Yeast two-hybrid and bimolecular fluorescence complementation indicated that ZmOSCA2.3 and ZmOSCA2.4 proteins interacted with ZmEREB198. Over-expression of ZmOSCA2.4 in Arabidopsis remarkably improved drought resistance. Moreover, over-expression of ZmOSCA2.4 enhanced the expression of drought tolerance-associated genes and reduced the expression of senescence-associated genes. We also found that perhaps ZmOSCA2.4 was regulated by miR5054.The results provide a high-quality molecular resource for selecting resistant breeding, and lay a foundation for elucidating regulatory mechanism of ZmOSCA under abiotic stresses.

Functional Analysis of Tadhn1312 by Virus-Induced Gene Silencing (VIGS) in Common Wheat ( Triticum aestivum L.)

The basic leucine zipper (bZIP) family of transcription factors (TFs) regulate diverse phenomena during plant growth and development and are involved in stress responses and hormone signaling. However, only a few bZIPs have been functionally characterized. In this paper, 54 maize bZIP genes were screened from previously published drought and rewatering transcriptomes. These genes were divided into nine groups in a phylogenetic analysis, supported by motif and intron/exon analyses. The 54 genes were unevenly distributed on 10 chromosomes and contained 18 segmental duplications, suggesting that segmental duplication events have contributed to the expansion of the maize bZIP family. Spatio-temporal expression analyses showed that bZIP genes are widely expressed during maize development. We identified 10 core ZmbZIPs involved in protein transport, transcriptional regulation, and cellular metabolism by principal component analysis, gene co-expression network analysis, and Gene Ontology enrichment analysis. In addition, 15 potential stress-responsive ZmbZIPs were identified by expression analyses. Localization analyses showed that ZmbZIP17, -33, -42, and -45 are nuclear proteins. These results provide the basis for future functional genomic studies on bZIP TFs in maize and identify candidate genes with potential applications in breeding/genetic engineering for increased stress resistance. These data represent a high-quality molecular resource for selecting resistant breeding materials.

Drought can severely limit plant growth and production. However, few studies have investigated gene expression profiles in maize during drought/re-watering. We compared drought-treated and water-sufficient maize plants by measuring their leaf relative water content, superoxide dismutase and peroxidase activities, proline content, and leaf gas exchange parameters (photosynthetic rates, stomatal conductance, and transpiration rates). We conducted RNA sequencing analyses to elucidate gene expression profiles and identify miRNAs that might be related to drought resistance. A GO enrichment analysis showed that the common DEGs (differently expressed genes) between drought-treated and control plants were involved in response to stimulus, cellular process, metabolic process, cell part, and binding and catalytic activity. Analyses of gene expression profiles revealed that 26 of the DEGs under drought encoded 10 enzymes involved in proline synthesis, suggesting that increased proline synthesis was a key part of the drought response. We also investigated cell wall-related genes and transcription factors regulating abscisic acid-dependent and -independent pathways. The expression profiles of the miRNAs miR6214-3p, miR5072-3p, zma-miR529-5p, zma-miR167e-5p, zma-miR167f-5p, and zma-miR167j-5p and their relevant targets under drought conditions were analyzed. These results provide new insights into the molecular mechanisms of drought tolerance, and may identify new targets for breeding drought-tolerant maize lines. Abbreviations: leaf relative water content: RWC, superoxide dismutase activity: SOD, peroxidase activity: POD, proline content: Pro, photosynthetic rates: Pn, stomatal conductance: Cond, transpiration rates: Tr.; quantitative real-time polymerase chain reaction: qPCR; abscisic acid; ABA; polyethylene glycol :PEG; Principal component analysis :PCA; polyacrylamide gel electrophoresis :PAGE Highlight: The study of physiology and molecular mechanism of maize laid a theoretical foundation for drought resistance breeding under drought stress and re-watering.