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Title: Proper regulation of a sperm-specific cis-nat-siRNA is essential for double fertilization in Arabidopsis

item RON, MILY - University Of California
item ALANDETE-SAEZ, MONICA - University Of California
item WILLIAMS, LEONOR - Hebrew University Of Jerusalem
item Fletcher, Jennifer
item McCormick, Sheila

Submitted to: Genes and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2010
Publication Date: 5/15/2010
Citation: Ron, M., Alandete-Saez, M., Williams, L.C., Fletcher, J.C., Mccormick, E.J. 2010. Proper regulation of a sperm-specific cis-nat-siRNA is essential for double fertilization in Arabidopsis. Genes and Development. 24(10):24: 1010-1021.

Interpretive Summary: Gene regulation by small RNAs is widespread. One category of small RNAs are cis-nat-siRNAs, which are generated from overlapping transcripts of two genes with opposite orientations. We show that regulation of a sperm-expressed gene by a cis-nat-siRNA is important for double fertilization in Arabidopsis thaliana, a plant often used as a model organism.

Technical Abstract: /Cis/-nat-siRNAs are a recently characterized class of small regulatory RNAs that are widespread in eukaryotes. Despite their abundance the importance of their regulatory activity is largely unknown. The only functional role for eukaryotic /cis/-nat-siRNAs that has been described to date is in environmental stress responses in plants. Here we demonstrate that /cis/-nat-siRNA-based regulation plays key roles in Arabidopsis reproductive function, as it facilitates both gametophyte formation and double fertilization, a developmental process of enormous agricultural value. We show that male gametophytic /kokopelli/ (/kpl/) mutants display frequent single fertilization events, and that /KPL/ and a inversely transcribed gene, /ARIADNE14 (ARI14)/, which encodes a putative ubiquitin-E3 ligase, generate a sperm-specific nat-siRNA pair. In the absence of /KPL/, /ARI14/ RNA levels in sperm are increased and fertilization is impaired. Furthermore,/ ARI14/ transcripts accumulate in several siRNA biogenesis pathway mutants and over-expression of /ARI14 /in sperm/ /phenocopies the reduced seed set of the /kokopelli/ mutants. These results extend the regulatory capacity of /cis/-nat-siRNAs to development by identifying a role for /cis/-nat-siRNAs in controlling sperm function during double fertilization.