CARPEL FACTORY, a Dicer homolog, and HEN1, a novel protein, act in microRNA metabolism in Arabidopsis thaliana.
BACKGROUND
In metazoans, microRNAs, or miRNAs, constitute a growing family of small regulatory RNAs that are usually 19-25 nucleotides in length. They are processed from longer precursor RNAs that fold into stem-loop structures by the ribonuclease Dicer and are thought to regulate gene expression by base pairing with RNAs of protein-coding genes. In Arabidopsis thaliana, mutations in CARPEL FACTORY (CAF), a Dicer homolog, and those in a novel gene, HEN1, result in similar, multifaceted developmental defects, suggesting a similar function of the two genes, possibly in miRNA metabolism.


RESULTS
To investigate the potential functions of CAF and HEN1 in miRNA metabolism, we aimed to isolate miRNAs from Arabidopsis and examine their accumulation during plant development in wild-type plants and in hen1-1 and caf-1 mutant plants. We have isolated 11 miRNAs, some of which have potential homologs in tobacco, rice, and maize. The putative precursors of these miRNAs have the capacity to form stable stem-loop structures. The accumulation of these miRNAs appears to be spatially or temporally controlled in plant development, and their abundance is greatly reduced in caf-1 and hen1-1 mutants. HEN1 homologs are found in bacterial, fungal, and metazoan genomes.


CONCLUSIONS
miRNAs are present in both plant and animal kingdoms. An evolutionarily conserved mechanism involving a protein, known as Dicer in animals and CAF in Arabidopsis, operates in miRNA metabolism. HEN1 is a new player in miRNA accumulation in Arabidopsis, and HEN1 homologs in metazoans may have a similar function. The developmental defects associated with caf-1 and hen1-1 mutations and the patterns of miRNA accumulation suggest that miRNAs play fundamental roles in plant development.
Park
Wonkeun
W
Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA.
Li
Junjie
J
Song
Rentao
R
Messing
Joachim
J
Chen
Xuemei
X
D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D004722:Endoribonucleases / Q000235:genetics / Q000502:physiology*; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D035683:MicroRNAs / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D018749:RNA, Plant / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D043244:Ribonuclease III; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C450825:HEN1 protein, Arabidopsis; D035683:MicroRNAs; D012322:RNA Precursors; D018749:RNA, Plant; D004722:Endoribonucleases; C402383:DCL1 protein, Arabidopsis; D043244:Ribonuclease III