microRNA-mediated repression of rolled leaf1 specifies maize leaf polarity.
In both animals and plants, many developmentally important regulatory genes have complementary microRNAs (miRNAs), which suggests that these miRNAs constitute a class of developmental signalling molecules. Leaves of higher plants exhibit a varying degree of asymmetry along the adaxial/abaxial (upper/lower) axis. This asymmetry is specified through the polarized expression of class III homeodomain/leucine zipper (HD-ZIPIII) genes. In Arabidopsis, three such genes, PHABULOSA (PHB), PHAVOLUTA (PHV) and REVOLUTA (REV), are expressed throughout the incipient leaf, but become adaxially localized after primordium emergence. Downregulation of the HD-ZIPIII genes allows expression of the KANADI and YABBY genes, which specify abaxial fate. PHB, PHV and REV transcripts contain a complementary site for miRNA165 and miRNA166, which can direct their cleavage in vitro. Here we show that miRNA166 constitutes a highly conserved polarizing signal whose expression pattern spatially defines the expression domain of the maize hd-zipIII family member rolled leaf1 (rld1). Moreover, the progressively expanding expression pattern of miRNA166 during leaf development and its accumulation in phloem suggests that miRNA166 may form a movable signal that emanates from a signalling centre below the incipient leaf.
Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Michelle T
MT
Juarez
Jonathan S
JS
Kui
Julie
J
Thomas
Bradley A
BA
Heller
Marja C P
MC
Timmermans
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D019521:Body Patterning; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D018515:Plant Leaves / Q000196:embryology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000196:embryology* / Q000235:genetics*
D035683:MicroRNAs; D010940:Plant Proteins; D018749:RNA, Plant