title: A novel class of bacteria-induced small RNAs in Arabidopsis.
abstract: Small RNAs, including microRNAs (miRNAs) and small interfering RNAs (siRNAs), are essential regulatory molecules of many cellular processes. Arabidopsis has at least three classes of endogenous siRNAs--chromatin-associated siRNAs, trans-acting siRNAs (tasiRNAs), and natural antisense transcript (NAT)-associated siRNAs (nat-siRNAs)--all 20-25 nucleotides (nt) in length. Here, we identified a novel class of small RNAs, long siRNAs (lsiRNAs), which are 30-40 nt and share many common features with known siRNAs. The lsiRNAs identified so far are induced by pathogen infection or under specific growth conditions. One of the lsiRNAs, AtlsiRNA-1, is generated from SRRLK/AtRAP NAT pair and specifically induced by the bacterium Pseudomonas syringae carrying effector avrRpt2. Recently, 25- to 31-nt PIWI-interacting RNAs (piRNAs) and repeat-associated siRNAs (rasiRNAs) were identified in animal germline cells. In contrast to the biogenesis of piRNAs/rasiRNAs, which is dicer independent and requires PIWI subfamily proteins, generation of AtlsiRNA-1 requires DCL1, DCL4, and the ARGONAUTE subfamily protein AGO7. It also depends on HYL1, HEN1, HST1, RDR6, and Pol IV. Induction of AtlsiRNA-1 silences AtRAP, which encodes a RAP-domain protein involved in disease resistance. Our further analysis implies that AtlsiRNA-1 may destabilize target mRNA through decapping and XRN4-mediated 5'-to-3' degradation.
authors.affiliation: Department of Plant Pathology and Microbiology, Center for Plant Cell Biology and Institute for Integrative Genome Biology, University of California at Riverside, Riverside, California 92521, USA.
authors.forename: Surekha
authors.initials: S
authors.lastname: Katiyar-Agarwal
authors.forename: Shang
authors.initials: S
authors.lastname: Gao
authors.forename: Adam
authors.initials: A
authors.lastname: Vivian-Smith
authors.forename: Hailing
authors.initials: H
authors.lastname: Jin
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D035683:MicroRNAs / Q000096:biosynthesis / Q000145:classification / Q000235:genetics*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity; D020871:RNA Stability; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000145:classification / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D035683:MicroRNAs; D034741:RNA, Small Interfering