MicroRNAs (miRNAs) are ~21-nucleotide-long regulatory RNAs that arise from endonucleolytic processing of hairpin precursors. Many function as essential posttranscriptional regulators of target mRNAs ...and long noncoding RNAs. Alongside miRNAs, plants also produce large numbers of short interfering RNAs (siRNAs), which are distinguished from miRNAs primarily by their biogenesis (typically processed from long double-stranded RNA instead of single-stranded hairpins) and functions (typically via roles in transcriptional regulation instead of posttranscriptional regulation). Next-generation DNA sequencing methods have yielded extensive data sets of plant small RNAs, resulting in many miRNA annotations. However, it has become clear that many miRNA annotations are questionable. The sheer number of endogenous siRNAs compared with miRNAs has been a major factor in the erroneous annotation of siRNAs as miRNAs. Here, we provide updated criteria for the confident annotation of plant miRNAs, suitable for the era of “big data” from DNA sequencing. The updated criteria emphasize replication and the minimization of false positives, and they require next-generation sequencing of small RNAs. We argue that improved annotation systems are needed for miRNAs and all other classes of plant small RNAs. Finally, to illustrate the complexities of miRNA and siRNA annotation, we review the evolution and functions of miRNAs and siRNAs in plants.
Plant cells accumulate small RNA molecules that regulate plant development, genome stability, and environmental responses. These small RNAs fall into three major classes based on their function and ...mechanisms of biogenesis-microRNAs, heterochromatic small interfering RNAs, and secondary small interfering RNAs-plus several other less well-characterized categories. Biogenesis of each small RNA class requires a pathway of factors, some specific to each pathway and others involved in multiple pathways. Diverse sequenced plant genomes, along with rapid developments in sequencing, imaging, and genetic transformation techniques, have enabled significant progress in understanding the biogenesis, functions, and evolution of plant small RNAs, including those that had been poorly characterized because they were absent or had low representation in
Arabidopsis
(
Arabidopsis thaliana
). Here, we review recent findings about plant small RNAs and discuss our current understanding of their biogenesis mechanisms, targets, modes of action, mobility, and functions in
Arabidopsis
and other plant species, including economically important crops.
Vulval squamous cell carcinoma (VSCC) can arise through two distinct pathways human papillomavirus (HPV)‐associated and HPV‐independent, and these VSCC variants are recognised as different disease ...entities on the basis of different aetiologies, morphological features, molecular events during oncogenesis, precursor lesions, prognosis, and response to treatment. The precursor of HPV‐associated VSCC, variously referred to as high‐grade squamous intraepithelial lesion (HSIL) vulvar intraepithelial neoplasia (VIN) 2/3 or usual‐type VIN, is morphologically identical to the more common HSIL (cervical intraepithelial neoplasia 2/3) of the cervix. The precursor lesions of HPV‐independent VSCC include differentiated VIN, differentiated exophytic vulvar intraepithelial lesion, and vulvar acanthosis with altered differentiation; these have been under‐recognised by pathologists in the past, leading to delays in treatment. This review will discuss the recent advances in diagnostic surgical pathology of VSCC and its precursors, and how these diagnoses can impact on patient management.
In plants, miR390 directs the production of tasiRNAs from TRANS-ACTING SIRNA3 (TAS3) transcripts to regulate AUXIN RESPONSIVE FACTOR (ARF) genes, critical for auxin signaling; these tasiRNAs are ...known as tasiARFs. To understand the evolution of this miR390-TAS3-ARF pathway, we characterized homologs of these three genes from thousands of plant species, from bryophytes to angiosperms. We found the lower-stem region of MIR390 genes, critical for accurate DICER-LIKE1 processing, is conserved in sequence in seed plants. We propose a model for the transition of functional tasiRNA sequences in TAS3 genes occurred at the emergence of vascular plants, in which the two miR390 target sites of TAS3 genes showed distinct pairing patterns. Based on the cleavability of miR390 target sites and the distance between target site and tasiARF, we inferred a potential bidirectional processing mechanism exists for some TAS3 genes. We also demonstrated a tight mutual selection between tasiARF and its target genes and that ARGONAUTE7, the partner of miR390, was specified later than other factors in the pathway. All these data illuminate the evolutionary path of the miR390-TAS3-ARF pathway in land plants and demonstrate the significant variation that occurs in this functionally important and archetypal regulatory circuit.
An updated World Health Organization (WHO) classification of female genital tumours was published in autumn 2020. We discuss the major new additions to and changes from the prior 2014 classification ...with a discussion of the reasons underlying these. A feature of the new classification is the greater emphasis on key molecular events with integration of morphological and molecular features. Most of the major changes from the prior classification pertain to uterine (corpus and cervix) and vulval tumours, but changes in all organs are covered.
We review the major new additions and changes in the new 2020 WHO Classification of Female Genital Tract Tumours. The updated 2020 Classification places a greater emphasis on key molecular events and on the integration of morphological and molecular features and represents a major step‐forward from the prior Classification.
Phased secondary small interfering RNAs (phasiRNAs) constitute a major category of small RNAs in plants, but most of their functions are still poorly defined. Some phasiRNAs, known as
-acting siRNAs, ...are known to target complementary mRNAs for degradation and to function in development. However, the targets or biological roles of other phasiRNAs remain speculative. New insights into phasiRNA biogenesis, their conservation, and their variation across the flowering plants continue to emerge due to the increased availability of plant genomic sequences, deeper and more sophisticated sequencing approaches, and improvements in computational biology and biochemical/molecular/genetic analyses. In this review, we survey recent progress in phasiRNA biology, with a particular focus on two classes associated with male reproduction: 21-nucleotide (accumulate early in anther ontogeny) and 24-nucloetide (produced in somatic cells during meiosis) phasiRNAs. We describe phasiRNA biogenesis, function, and evolution and define the unanswered questions that represent topics for future research.
Spin dynamics in antiferromagnets has much shorter timescales than in ferromagnets, offering attractive properties for potential applications in ultrafast devices
. However, spin-current generation ...via antiferromagnetic resonance and simultaneous electrical detection by the inverse spin Hall effect in heavy metals have not yet been explicitly demonstrated
. Here we report sub-terahertz spin pumping in heterostructures of a uniaxial antiferromagnetic Cr
O
crystal and a heavy metal (Pt or Ta in its β phase). At 0.240 terahertz, the antiferromagnetic resonance in Cr
O
occurs at about 2.7 tesla, which excites only right-handed magnons. In the spin-canting state, another resonance occurs at 10.5 tesla from the precession of induced magnetic moments. Both resonances generate pure spin currents in the heterostructures, which are detected by the heavy metal as peaks or dips in the open-circuit voltage. The pure-spin-current nature of the electrically detected signals is unambiguously confirmed by the reversal of the voltage polarity observed under two conditions: when switching the detector metal from Pt to Ta, reversing the sign of the spin Hall angle
, and when flipping the magnetic-field direction, reversing the magnon chirality
. The temperature dependence of the electrical signals at both resonances suggests that the spin current contains both coherent and incoherent magnon contributions, which is further confirmed by measurements of the spin Seebeck effect and is well described by a phenomenological theory. These findings reveal the unique characteristics of magnon excitations in antiferromagnets and their distinctive roles in spin-charge conversion in the high-frequency regime.
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