Proper regulation of a sperm-specific cis-nat-siRNA is essential for double fertilization in Arabidopsis.
Natural cis-antisense siRNAs (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 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 overexpression 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.
Ron
Mily
M
Department of Plant and Microbial Biology, Plant Gene Expression Center, US Department of Agriculture/Agricultural Research Service, University of California at Berkeley, Albany, California 94710, USA.
Alandete Saez
Monica
M
Eshed Williams
Leor
L
Fletcher
Jennifer C
JC
McCormick
Sheila
S
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D005306:Fertilization / Q000235:genetics*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D009154:Mutation / Q000235:genetics; D056771:Ovule / Q000254:growth & development; D010641:Phenotype; D011058:Pollen / Q000235:genetics; D016372:RNA, Antisense / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000378:metabolism*
D029681:Arabidopsis Proteins; D016372:RNA, Antisense; D034741:RNA, Small Interfering