Plant productivity is greatly affected by environmental stresses such as drought, salt loading, and freezing. We reported previously that a cis-acting promoter element, the dehydration response element (DRE), plays an important role in regulating gene expression in response to these stresses. The transcription factor DREB1A specifically interacts with the DRE and induces expression of stress tolerance genes. We show here that overexpression of the cDNA encoding DREB1A in transgenic plants activated the expression of many of these stress tolerance genes under normal growing conditions and resulted in improved tolerance to drought, salt loading, and freezing. However, use of the strong constitutive 35S cauliflower mosaic virus (CaMV) promoter to drive expression of DREB1A also resulted in severe growth retardation under normal growing conditions. In contrast, expression of DREB1A from the stress inducible rd29A promoter gave rise to minimal effects on plant growth while providing an even greater tolerance to stress conditions than did expression of the gene from the CaMV promoter.

;The transcription factors DREB1s/CBFs specifically interact with the DRE/CRT cis-acting element (core motif: G/ACCGAC) and control the expression of many stressinducible genes in Arabidopsis. We isolated a cDNA for a DREB1/CBF homolog, ZmDREB1A in maize using a yeast one-hybrid system. The ZmDREB1A proteins specifically bound to DRE and the highly conserved valine at the 14th residue in the ERF/AP2 DNA binding domain was a key to determining the specific interaction between this protein and the DRE sequence. Expression of ZmDREB1A was induced by cold stress and slightly increased by highsalinity stress. This gene was also transiently expressed by mechanical attack. ZmDREB1A activated the transcription of the GUS reporter gene driven by DRE in rice protoplasts. Overexpression of ZmDREB1A in transgenic Arabidopsis induced overexpression of target stress-inducible genes of Arabidopsis DREB1A resulting in plants with higher tolerance to drought and freezing stresses. This indicated that ZmDREB1A has functional similarity to DREB1s/CBFs in Arabidopsis. The structure of the ERF/ AP2 domain of ZmDREB1A in maize is closely related to DREB1-type ERF/AP2 domains in the monocots as compared with that in the dicots. ZmDREB1A is suggested to be potentially useful for producing transgenic plants that is tolerant to drought, high-salinity and/or cold stresses.

No abstract

Environmental stresses, such as salinity, drought and cold, can induce the expression of a large amount of genes. Among these are many transcription factors that regulate the expression of downstream genes by specifically binding to cis-elements or forming transcriptional complexes with other proteins. In the present study, a DREB-like transcription factor gene, named AhDREB1, was isolated from a halophyte Atriplex hortensis. AhDREB1 encoded a protein containing a conserved EREBP/AP2 domain featuring the DREB family. In yeast one-hybrid analysis AhDREB1 protein was specifically bound to DRE elements and activated the expression of the reporter genes of HIS3 and LacZ. The AhDREB1 gene was expressed in roots, stems and leaves of A. hortensis. Salinity induced its expression in roots, but not in other organs. Overexpression of AhDREB1 in transgenic tobacco led to the accumulation of its putative downstream genes. The performance of the transgenic lines was also tested under stressed conditions and two lines were found to be stress-tolerant. These results suggest that the AhDREB1 protein functions as a DRE-binding transcription factor and play roles in the stress-tolerant response of A. hortensis.

Abstract. Infertility is a significant problem for human reproduction, with males and females equally affected. However, the molecular mechanisms underlying male infertility remain unclear. Spermatogenesis is a highly complex process involving mitotic cell division, meiosis cell division and spermiogenesis; during this period, unique and extensive chromatin and epigenetic modifications occur to bring about specific epigenetic profiles in spermatozoa. It has recently been suggested that the dysregulation of epigenetic modifications, in particular the methylation of sperm genomic DNA, may serve an important role in the development of numerous diseases. The present study is a comprehensive review on the topic of male infertility, aiming to elucidate the association between sperm genomic DNA methylation and poor semen quality in male infertility. In addition, the current status of the genetic and epigenetic determinants of spermatogenesis in humans is discussed. Contents1. Introduction 2. DNA methylation 3. DNA methylation and spermatogenesis 4. DNA methylation and genomic imprinting 5. DNA methylation and male infertility 6. Conclusion IntroductionEpigenetics is the study of genomic structural modifications that affect gene expression without altering the underlying nucleotide sequence (1-3). Epigenetic mechanisms involved in the regulation of gene expression include the regulation of non-coding RNA, chromatin remodeling, DNA methylation and histone modifications (4,5). Of these mechanisms, DNA methylation has been implicated in numerous biological functions, such as the development of spermatozoa and early embryos, and the repression of endogenous retrotransposons, while it also has a wide range of effects in gene expression (2,3,6). The dysregulation of DNA methylation has previously been associated with various human disorders, and has been shown to increase the risk of fertilization failure, dysfunction in embryogenesis, perinatal mortality, congenital abnormalities, preterm birth and low birth weight (7-11). The present review assesses the significance of DNA methylation in spermatogenesis in order to elucidate the association between the dysregulation of DNA methylation and male infertility. This may provide a basis for the prevention and treatment of male infertility, as well as permit the evaluation of the epigenetic quality of sperm in order to reduce the risk of epigenetic diseases in cases where conception is performed by assisted reproductive technology (ART). DNA methylationEpigenetic mechanisms are critical regulators of gene expression during spermatogenesis that may influence male fertility (12-14). Cytosine, a key DNA base, is methylated at the position, typically in the context of CpG dinucleotides. The methylation of constitutive heterochromatic and promoter regions is generally associated with reduced gene transcription (Fig. 1A) (15-18). Therefore, DNA methylation is a type of epigenetic modification that can effectively promote gene silencing (Fig. 1B). The methyl group for this chemical modif...

Dissecting the genetic regulation of gene expression is critical for understanding phenotypic variation and species evolution. However, our understanding of the transcriptional variability in sweet potato remains limited. Here, we analyzed two publicly available datasets to explore the landscape of transcriptomic variations and its genetic basis in the storage roots of sweet potato. The comprehensive analysis identified a total of 724,438 high-confidence single nucleotide polymorphisms (SNPs) and 26,026 expressed genes. Expression quantitative trait locus (eQTL) analysis revealed 4408 eQTLs regulating the expression of 3646 genes, including 2261 local eQTLs and 2147 distant eQTLs. Two distant eQTL hotspots were found with target genes significantly enriched in specific functional classifications. By combining the information from regulatory network analyses, eQTLs and association mapping, we found that IbMYB1-2 acts as a master regulator and is the major gene responsible for the activation of anthocyanin biosynthesis in the storage roots of sweet potato. Our study provides the first insight into the genetic architecture of genome-wide expression variation in sweet potato and can be used to investigate the potential effects of genetic variants on key agronomic traits in sweet potato.

Abstract:High-resolution measurements of rainfall, water level, pH, conductivity, temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the Guilin Karst Experimental Site in Guangxi Province, China, were made with different types of multiparameter sonde. The data were stored using data loggers recording with 2 min or 15 min resolution. Waters from a large, perennial spring represent the exit for the aquifer's conduit flow, and a nearby well measures water in the conduit-adjacent, fractured media. During flood pulses, the pH of the conduit flow water rises as the conductivity falls. In contrast, and at the same time, the pH of groundwater in the fractures drops, as conductivity rises. As Ca 2C and HCO 3 were the dominant (>90%) ions, we developed linear relationships (both r 2 > 0Ð91) between conductivity and those ions, respectively, and in turn calculated variations in the calcite saturation index SI C and CO 2 partial pressure P CO 2 of water during flood pulses. Results indicate that the P CO 2 of fracture water during flood periods is higher than that at lower flows, and its SI C is lower. Simultaneously, P CO 2 of conduit water during the flood period is lower than that at lower flows, and its SI C also is lower. From these results we conclude that at least two key processes are controlling hydrochemical variations during flood periods: (i) dilution by precipitation and (ii) water-rock-gas interactions. To explain hydrochemical variations in the fracture water, the water-rock-gas interactions may be more important. For example, during flood periods, soil gas with high CO 2 concentrations dissolves in water and enters the fracture system, the water, which in turn has become more highly undersaturated, dissolves more limestone, and the conductivity increases. Dilution of rainfall is more important in controlling hydrochemical variations of conduit water, because rainfall with higher pH (in this area apparently owing to interaction with limestone dust in the lower atmosphere) and low conductivity travels through the conduit system rapidly. These results illustrate that to understand the hydrochemical variations in karst systems, considering only water-rock interactions is not sufficient, and the variable effects of CO 2 on the system should be evaluated. Consideration of water-rock-gas interactions is thus a must in understanding variations in karst hydrochemistry.

No abstract