Meiosis is unusual among cell divisions in shuffling genetic material by crossovers among homologous chromosomes and partitioning the genome into haploid gametes. Crossovers are critical for ...chromosome segregation in most eukaryotes, but are also an important factor in evolution, as they generate novel genetic combinations. The molecular mechanisms that underpin meiotic recombination and chromosome segregation are well conserved across kingdoms, but are also sensitive to perturbation by environment, especially temperature. Even subtle shifts in temperature can alter the number and placement of crossovers, while at greater extremes, structural failures can occur in the linear axis and synaptonemal complex structures which are essential for recombination and chromosome segregation. Understanding the effects of temperature on these processes is important for its implications in evolution and breeding, especially in the context of global warming. In this review, we first summarize the process of meiotic recombination and its reliance on axis and synaptonemal complex structures, and then discuss effects of temperature on these processes and structures. We hypothesize that some consistent effects of temperature on recombination and meiotic thermotolerance may commonly be two sides of the same coin, driven by effects of temperature on the folding or interaction of key meiotic proteins.
This article is part of the themed issue ‘Evolutionary causes and consequences of recombination rate variation in sexual organisms’.
To meet the demand of noise reduction in millimeter‐wave human body security imaging, this paper proposes a new method for 3D segmentation denoising in millimeter‐wave images. The test results ...indicate that with the incorporation of 3D segmentation denoising technology, the noise in the background area of millimeter wave images has decreased by approximately 20–40 dB, significantly improving image quality. The detection rate has increased from 90% to 95%, while the false positive rate has decreased from 13% to 5%. This has important practical significance for real‐world applications.
To meet the demand of noise reduction in millimeter‐wave human body security imaging, this paper proposes a new method for 3D segmentation denoising in millimeter‐wave images. The test results indicate that with the incorporation of 3D segmentation denoising technology, the noise in the background area of millimeter wave images has decreased by approximately 20–40 dB, significantly improving image quality. The detection rate has increased from 90% to 95%, while the false positive rate has decreased from 13% to 5%. This has important practical significance for real‐world applications.
Allopolyploidization has occurred frequently within the Triticum–Aegilops complex which provides a suitable system to investigate how allopolyploidization shapes the expression patterns of duplicated ...homeologs. We have conducted transcriptome‐profiling of leaves and young inflorescences in wild and domesticated tetraploid wheats, Triticum turgidum ssp. dicoccoides (BBAA) and ssp. durum (BBAA), an extracted tetraploid (BBAA), and a synthetic tetraploid (SˡSˡAA) wheat together with its diploid parents, Aegilops longissima (SˡSˡ) and Triticum urartu (AA). The two diploid species showed tissue‐specific differences in genome‐wide ortholog expression, which plays an important role in transcriptome shock‐mediated homeolog expression rewiring and hence transcriptome asymmetry in the synthetic tetraploid. Further changes of homeolog expression apparently occurred in natural tetraploid wheats, which led to novel transcriptome asymmetry between the two subgenomes. In particular, our results showed that extremely biased homeolog expression can occur rapidly upon the allotetraploidzation and this trend is further enhanced in the course of domestication and evolution of polyploid wheats. Our results suggest that allopolyploidization is accompanied by distinct phases of homeolog expression changes, with parental legacy playing major roles in the immediate rewiring of homeolog expression upon allopolyploidization, while evolution and domestication under allotetraploidy drive further homeolog‐expression changes toward re‐established subgenome expression asymmetry.
Nucleotide composition is suggested to infer gene functionality and ecological adaptation of species to distinct environments. However, the underlying biological function of nucleotide composition ...dictating environmental adaptations is largely unknown. Here, we systematically analyze the nucleotide composition of transcriptomes across 1000 plants (1KP) and their corresponding habitats. Intriguingly, we find that plants growing in cold climates have guanine (G)-enriched transcriptomes, which are prone to forming RNA G-quadruplex structures. Both immunofluorescence detection and in vivo structure profiling reveal that RNA G-quadruplex formation in plants is globally enhanced in response to cold. Cold-responsive RNA G-quadruplexes strongly enhanced mRNA stability, rather than affecting translation. Disruption of individual RNA G-quadruplex promotes mRNA decay in the cold, leading to impaired plant cold response. Therefore, we propose that plants adopted RNA G-quadruplex structure as a molecular signature to facilitate their adaptation to the cold during evolution.
Real-time video-rate passive terahertz imaging systems are highly demanded for practical applications, especially in security checking. Here, we demonstrate a passive video-rate terahertz human body ...imaging system, which was mainly consisted of a scanning module, a quasi-optical lens, a calibration module and a one-dimensional terahertz detector array. The terahertz waves radiated from human bodies in front of the imager can transmit through a terahertz window into the imager, and were reflected by the scanning module, and then focused on the detector array by the quasi-optical lens. A calibration module was also designed to calibrate the terahertz detectors in real-time without disturbing the imaging process. In combination of the scanning module with the detector array, the imager can obtain a full image of a human body standing at a distance of 1.5 m in front of the imager with a resolution of 1.5 cm and a frame rate of 10 fps. The imaging system can discover suspected dangerous items carried on the human body such as metals, ceramics, powders and liquids. Furthermore, an intelligent terahertz imaging algorithm employing convolutional neural network was also successfully realized based on the terahertz images produced by this system to improve the image quality and mark the detected items automatically. We believe our real-time video-rate terahertz imaging techniques and systems not only have great values for further inspiring developing terahertz imaging systems but also can accelerate the terahertz technology towards more practical applications.
Hexaploid bread wheat (Triticum aestivum L., genome BBAADD) is generally more salt tolerant than its tetraploid wheat progenitor (Triticum turgidum L.). However, little is known about the ...physiological basis of this trait or about the relative contributions of allohexaploidization and subsequent evolutionary genetic changes on the trait development. Here, we compared the salt tolerance of a synthetic allohexaploid wheat (neo-6 x) with its tetraploid (T. turgidum ; BBAA) and diploid (Aegilops tauschii; DD) parents, as well as a natural hexaploid bread wheat (nat-6 x). We studied 92 morphophysiological traits and analyzed homeologous gene expression of a major salt-tolerance gene High-Affinity K ⁺ Transporter 1;5 (HKT1;5). We observed that under salt stress, neo-6 x exhibited higher fitness than both of its parental genotypes due to inheritance of favorable traits like higher germination rate from the 4 x parent and the stronger root Na ⁺ retention capacity from the 2 x parent. Moreover, expression of the D-subgenome HKT1;5 homeolog, which is responsible for Na ⁺ removal from the xylem vessels, showed an immediate transcriptional reprogramming following allohexaploidization, i.e., from constitutive high basal expression in Ae. tauschii (2 x) to salt-induced expression in neo-6 x . This phenomenon was also witnessed in the nat-6 x . An integrated analysis of 92 traits showed that, under salt-stress conditions, neo-6 x resembled more closely the 2 x than the 4 x parent, suggesting that the salt stress induces enhanced expressivity of the D-subgenome homeologs in the synthetic hexaploid wheat. Collectively, the results suggest that condition-dependent functionalization of the subgenomes might have contributed to the wide-ranging adaptability of natural hexaploid wheat.
mRNA processing is critical for gene expression. A challenge in regulating mRNA processing is how to recognize the actual mRNA processing sites, such as splice and polyadenylation sites, when the ...sequence content is insufficient for this purpose. Previous studies suggested that RNA structure affects mRNA processing. However, the regulatory role of RNA structure in mRNA processing remains unclear.
Here, we perform in vivo selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) chemical profiling on Arabidopsis and generate the in vivo nuclear RNA structure landscape. We find that nuclear mRNAs fold differently from cytosolic mRNAs across translation start and stop sites. Notably, we discover a two-nucleotide single-stranded RNA structure feature upstream of 5' splice sites that is strongly associated with splicing and the selection of alternative 5' splice sites. The regulatory role of this RNA structure feature is further confirmed by experimental validation. Moreover, we find the single-strandedness of branch sites is also associated with 3' splice site recognition. We also identify an RNA structure feature comprising two close-by single-stranded regions that is specifically associated with both polyadenylation and alternative polyadenylation events.
We successfully identify pre-mRNA structure features associated with splicing and polyadenylation at whole-genome scale and validate an RNA structure feature which can regulate splicing. Our study unveils a new RNA structure regulatory mechanism for mRNA processing.
The continually growing human population creates a concomitantly increasing demand for nutritious crops with high yields. Advances in high throughput sequencing technologies have revealed the genetic ...architecture of major crops. This includes extensive information enabling comprehensive genetic markers for breeding selection, new gene discoveries, and novel gene regulatory strategies for crop editing. RNA structure is an important type of genetic feature, essential for post-transcriptional regulation of gene expression. Here, we summarize recent advances in genome-wide RNA structure studies in crops and review the associated RNA structure-mediated regulation of gene expression. We also discuss the functional importance of those single nucleotide variations that induce large RNA structure disparities. Lastly, we discuss the potential role of RNA structure in crop molecular breeding.
Allopolyploidization has been a driving force in plant evolution. Formation of common wheat (Triticum aestivum L.) represents a classic example of successful speciation via allopolyploidy. ...Nevertheless, the immediate chromosomal consequences of allopolyploidization in wheat remain largely unexplored. We report here an in-depth investigation on transgenerational chromosomal variation in resynthesized allohexaploid wheats that are identical in genome constitution to common wheat. We deployed sequential FISH, genomic in situ hybridization (GISH), and homeolog-specific pyrosequencing, which enabled unequivocal identification of each of the 21 homologous chromosome pairs in each of >1,000 individual plants from 16 independent lines. We report that whole-chromosome aneuploidy occurred ubiquitously in early generations (from selfed generation S ₁ to >S ₂₀) of wheat allohexaploidy although at highly variable frequencies (20–100%). In contrast, other types of gross structural variations were scant. Aneuploidy included an unexpected hidden type, which had a euploid chromosome number of 2 n = 42 but with simultaneous loss and gain of nonhomeologous chromosomes. Of the three constituent subgenomes, B showed the most lability for aneuploidy, followed by A, but the recently added D subgenome was largely stable in most of the studied lines. Chromosome loss and gain were also unequal across the 21 homologous chromosome pairs. Pedigree analysis showed no evidence for progressive karyotype stabilization even with multigenerational selection for euploidy. Profiling of two traits directly related to reproductive fitness showed that although pollen viability was generally reduced by aneuploidy, the adverse effect of aneuploidy on seed-set is dependent on both aneuploidy type and synthetic line.
Imprinting is an epigenetic phenomenon referring to allele‐biased expression of certain genes depending on their parent of origin. Accumulated evidence suggests that, while imprinting is a conserved ...mechanism across kingdoms, the identities of the imprinted genes are largely species‐specific. Using deep RNA sequencing of endosperm 14 days after pollination in sorghum, 5683 genes (29.27% of the total 19 418 expressed genes) were found to harbor diagnostic single nucleotide polymorphisms between two parental lines. The analysis of parent‐of‐origin expression patterns in the endosperm of a pair of reciprocal F₁ hybrids between the two sorghum lines led to identification of 101 genes with ≥ fivefold allelic expression difference in both hybrids, including 85 maternal expressed genes (MEGs) and 16 paternal expressed genes (PEGs). Thirty of these genes were previously identified as imprinted in endosperm of maize (Zea mays), rice (Oryza sativa) or Arabidopsis, while the remaining 71 genes are sorghum‐specific imprinted genes relative to these three plant species. Allele‐biased expression of virtually all of the 14 tested imprinted genes (nine MEGs and five PEGs) was validated by pyrosequencing using independent sources of RNA from various developmental stages and dissected parts of endosperm. Forty‐six imprinted genes (30 MEGs and 16 PEGs) were assayed by quantitative RT–PCR, and the majority of them showed endosperm‐specific or preferential expression relative to embryo and other tissues. DNA methylation analysis of the 5’ upstream region and gene body for seven imprinted genes indicated that, while three of the four PEGs were associated with hypomethylation of maternal alleles, no MEG was associated with allele‐differential methylation.
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