# DCL2
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{{Short description|Dicer-like gene in plants}}
{{Infobox nonhuman protein
| Name = Endoribonuclease Dicer homolog 2
| Symbol = DCL2
| UniProt = Q3EBC8
| Organism = Arabidopsis thaliana
| image = Dcl2.gif
| caption = Cartoon representation of Arabidopsis DCL2, Based on computational predictions using Alphafold2 and rendered with open software Mol Star * (https://alphafold.ebi.ac.uk/entry/Q3EBC8, https://molstar.org/viewer/)
| AltSymbols = AT3G03300
}}
'''DCL2''' (an abbreviation of '''Dicer-like 2''') is a [gene](/source/gene) in plants that codes for the DCL2 [protein](/source/protein), a [ribonuclease III](/source/ribonuclease_III) [enzyme](/source/enzyme) involved in processing exogenous [double-stranded RNA (dsRNA)](/source/Double-stranded_RNA) into 22 nucleotide [small interference RNAs](/source/Small_interfering_RNA) (siRNAs).[{{cite journal |vauthors=Jin L, Chen M, Xiang M, Guo Z |title=RNAi-Based Antiviral Innate Immunity in Plants |journal=Viruses |volume=14 |issue=2 |page=432 |date=February 2022 |pmid=35216025 |pmc=8875485 |doi=10.3390/v14020432 |doi-access=free}}]
Diverse sources of dsRNAs have been characterized, broadly classified as exogenous or endogenous. A classical example of exogenous derived dsRNAs are the viral genomes release during infection, specially from those [double-stranded RNA viruses](/source/double-stranded_RNA_viruses), where the cleavage of dsRNA produce small RNA products called [viral siRNAs](/source/viral_siRNAs) or vsi-RNAs.[{{cite journal |vauthors=Sanan-Mishra N, Abdul Kader Jailani A, Mandal B, Mukherjee SK |title=Secondary siRNAs in Plants: Biosynthesis, Various Functions, and Applications in Virology |journal=Frontiers in Plant Science |volume=12 |article-number=610283 |date=2021-03-02 |pmid=33737942 |pmc=7960677 |doi=10.3389/fpls.2021.610283 |bibcode=2021FrPS...1210283S |doi-access=free}}] Other examples of exogenous source of dsRNAs are [transgenic](/source/Transgene) with several insertion loci along the plant hos genome.[{{Cite journal |vauthors=Stam M |date=January 1997 |title=Review Article: The Silence of Genes in Transgenic Plants |journal=Annals of Botany |volume=79 |issue=1 |pages=3–12 |doi=10.1006/anbo.1996.0295|bibcode=1997AnBot..79....3S |doi-access=free }}] DCL2 also process endogenous sources as double-stranded RNAs derived of ''cis-''[natural antisense transcript](/source/natural_antisense_transcript)s, generating 22nt short interfering RNA (natsi-RNAs); however, the biological relevance, evolutionary conservation, and experimental validation of natsi-RNAs remains controversial.[{{Citation |vauthors=Meyers BC, Zhan J, Shevela D, Slotkin KR |title=Plant Small RNAs: Biogenesis and Functions, Agrisera Educational Poster Collection, Poster 6, 2022 |date=2022 |publisher=Figshare |url=https://figshare.com/articles/poster/Plant_Small_RNAs_Biogenesis_and_Functions_Agrisera_Educational_Poster_Collection_Poster_6_2022/21186073 |doi=10.6084/m9.figshare.21186073 |access-date=2022-11-06}}]
==Function==
Dicer proteins belongs to the RNaseIII-like family, a gene family with highly conserved endonuclease in eukaryotes, with procaryotes representatives.[{{cite journal |vauthors=Cenik ES, Fukunaga R, Lu G, Dutcher R, Wang Y, Tanaka Hall TM, Zamore PD |title=Phosphate and R2D2 restrict the substrate specificity of Dicer-2, an ATP-driven ribonuclease |language=English |journal=Molecular Cell |volume=42 |issue=2 |pages=172–184 |date=April 2011 |pmid=21419681 |pmc=3115569 |doi=10.1016/j.molcel.2011.03.002}}] In Arabidopsis and most of land Plants, there are mainly four Dicer-like proteins (DCL): [DCL1](/source/DCL1), DCL2, [DCL3](/source/DCL3), and [DCL4](/source/DCL4). They all contain five domains, following the order from N-terminus to C-terminus: [DEXD-helicase](/source/Helicase), helicase-C, [domain of unknown function](/source/domain_of_unknown_function) 283 (DUF283), Piwi/[Argonaute](/source/Argonaute)/Zwille (PAZ) domain, two tandem RNase III domains, and one or two dsRNA-binding domains (dsRBDs).[{{cite journal |vauthors=Szczepanska A, Wojnicka M, Kurzynska-Kokorniak A |title=The Significance of the DUF283 Domain for the Activity of Human Ribonuclease Dicer |journal=International Journal of Molecular Sciences |volume=22 |issue=16 |page=8690 |date=August 2021 |pmid=34445396 |pmc=8395393 |doi=10.3390/ijms22168690 |doi-access=free}}] The PAZ and RNase III domains are essential for dsRNA cleavage via the recognition of dsRNA ends by PAZ domain, the RNase III domains cuts one of the strands of dsRNA.[{{cite journal |vauthors=Welker NC, Pavelec DM, Nix DA, Duchaine TF, Kennedy S, Bass BL |title=Dicer's helicase domain is required for accumulation of some, but not all, C. elegans endogenous siRNAs |journal=RNA |volume=16 |issue=5 |pages=893–903 |date=May 2010 |pmid=20354150 |pmc=2856884 |doi=10.1261/rna.2122010}}]
DCL2 plays an essential role in transitive silencing of transgenes by processing [secondary siRNAs](/source/secondary_siRNAs), including [trans-acting siRNA](/source/trans-acting_siRNA).[{{Cite journal |vauthors=Benoit M |title=Slice and Dice: DCL2 Mediates the Production of 22-Nucleotide siRNAs that Influence Trait Variation in Soybean |journal=The Plant Cell |year=2020 |volume=32 |issue=12 |pages=3646–3647 |doi=10.1105/tpc.20.00884 |pmc=7721339 |pmid=33093146 |bibcode=2020PlanC..32.3646B }}]
==Transitive and systemic RNA silencing==
A key difference between DCL1 and others DCLs 2,3 and 4 proteins is the amplification capacity of the pathways specific for the later protein. The involvement of [RDR](/source/RNA-dependent_RNA_polymerase) proteins extends the small RNA-target complex beyond the original trigger-spot. The subset of siRNA used in signal amplification are called transitive or secondary siRNAs and the process of amplification is called transitivity.[{{cite journal |vauthors=Choudhary S, Thakur S, Bhardwaj P |title=Molecular basis of transitivity in plant RNA silencing |journal=Molecular Biology Reports |volume=46 |issue=4 |pages=4645–4660 |date=August 2019 |pmid=31098805 |doi=10.1007/s11033-019-04866-9 |s2cid=155103992}}] The amplification propagates the secondary siRNA and its target specific silencing activity from one tissue to another, eventually reaching the whole plant's tissues, in a process called [systemic silencing.](/source/systemic_silencing.)