A Conserved microRNA Signal Specifies Leaf Polarity

Timmermans, Marja C.P.; Juarez, Michelle T.; Phelps-Durr, T.L.

doi:10.1101/sqb.2004.69.50

Cited by 3 publications

(4 citation statements)

References 76 publications

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“…These observations indicate that lbl1 contributes to leaf polarity by regulating the adaxial expression of multiple hd-zipIII genes. Perhaps lbl1 regulates hd-zipIII expression at the transcriptional level; alternatively, because the hd-zipIII expression domain in the leaf is defined by miR166 (Juarez et al 2004a;Timmermans et al 2004), lbl1 could affect hd-zipIII expression through changes in the pattern of miR166 accumulation. To test this possibility, we analyzed expression of miR166 in lbl1-rgd1.…”

Section: Resultsmentioning

confidence: 99%

Two small regulatory RNAs establish opposing fates of a developmental axis

Nogueira¹,

Madi²,

Chitwood³

et al. 2007

Genes Dev.

241

268

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Small RNAs are important regulators of gene expression. In maize, adaxial/abaxial (dorsoventral) leaf polarity is established by an abaxial gradient of microRNA166 (miR166), which spatially restricts the expression domain of class III homeodomain leucine zipper (HD-ZIPIII) transcription factors that specify adaxial/upper fate. Here, we show that leafbladeless1 encodes a key component in the trans-acting small interfering RNA (ta-siRNA) biogenesis pathway that acts on the adaxial side of developing leaves and demarcates the domains of hd-zipIII and miR166 accumulation. Our findings indicate that tasiR-ARF, a ta-siRNA, and miR166 establish opposing domains along the adaxial-abaxial axis, thus revealing a novel mechanism of pattern formation.Supplemental material is available at www.genesdev.org.Received January 8, 2007; revised version accepted February 20, 2007. In both animals and plants, many developmentally important regulatory genes are predicted targets of microRNAs (miRNAs), which suggests that such small RNAs constitute a class of developmental determinants (Alvarez-Garcia and Miska 2005;Jones-Rhoades et al. 2006). Patterning and outgrowth of lateral organs in plants depend on the specification of adaxial/abaxial (dorsoventral) polarity in the incipient primordium. This asymmetry is established through the polarized expression of class III homeodomain leucine zipper (HD-ZIPIII) transcription factors that specify adaxial/upper cell fate (McConnell et al. 2001;Emery et al. 2003;Juarez et al. 2004a). The adaxial-specific expression of hd-zipIII family members is delineated by the expression pattern of a 21-nucleotide (nt) miRNA, miR166, which directs the cleavage of hd-zipIII transcripts (Juarez et al. 2004a;Kidner and Martienssen 2004). In maize, miR166 accumulates most abundantly immediately below the incipient leaf, but a gradient of miR166 extends into the abaxial side of the initiating organ that establishes organ polarity (Juarez et al. 2004a).Specification of adaxial/abaxial organ polarity in maize also requires the activity of leafbladeless1 (lbl1). Recessive mutations in lbl1 lead to a variable abaxialization of leaves (Timmermans et al. 1998). The weak lbl1-ref allele causes a partial loss of adaxial identity revealed as patches of abaxial cells on the upper leaf surface, whereas leaves of the severe ragged seedling1 allele (lbl1-rgd1) are often radially symmetric and completely abaxialized (Fig. 1A). Expression of the hd-zipIII family member rld1 is reduced in lbl1 mutants. Conversely, increased levels of hd-zipIII expression in Rld1-O mutants, which carry a miR166-insensitive allele of rld1, can fully suppress the vegetative defects of lbl1 (Juarez et al. 2004b). lbl1 thus contributes to organ polarity by regulating the accumulation of rld1 transcripts on the adaxial side of the developing leaf.Here, we show that lbl1 encodes a homolog of SUPPRESSOR-OF-GENE-SILENCING3 (SGS3), which is specifically required for the biogenesis of trans-acting small interfering RNAs (ta-siRNAs) (Peragine et al. 2...

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Section: Resultsmentioning

confidence: 99%

Two small regulatory RNAs establish opposing fates of a developmental axis

Nogueira¹,

Madi²,

Chitwood³

et al. 2007

Genes Dev.

241

268

View full text Add to dashboard Cite

show abstract

“…In P1 primordia, higher levels of miR166 accumulate abaxially and, in older primordia, miR166 accumulates in a progressively broader domain extending adaxially and laterally (Juarez et al 2004b). These findings suggest that miR165/166 is a highly conserved polarizing signal that specifies adaxial/abaxial polarity by restricting HD-ZIPIII expression to the adaxial side of the leaf in both dicots and monocots (Timmermans et al 2004). The spatial regulation of HD-ZIPIII gene expression by miR165/166 may even predate the origin of angiosperm leaves.…”

Section: Role Of Mirna165/166 In Adaxial/abaxial Patterningmentioning

confidence: 99%

“…The biogenesis and function of plant miRNAs have been extensively reviewed elsewhere (see Timmermans et al 2004;Jones-Rhoades et al 2006;Mallory and Vaucheret 2006). Briefly, miRNAs are processed from Figure 2.…”

Section: Biogenesis and Function Of Mirnasmentioning

confidence: 99%

Organ Polarity in Plants Is Specified through the Opposing Activity of Two Distinct Small Regulatory RNAs

Nogueira¹,

Sarkar²,

Chitwood³

et al. 2006

Cold Spring Harbor Symposia on Quantitative Biology

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“…However, very little is known about the cross talk between miRNA signals and hormones. In Arabidopsis, a number of miRNAs were identified, showing critical roles in developmental regulations [7,[10][11][12][13][14][15][16][17][18][19][20]. …”

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confidence: 99%

Plant fertility defects induced by the enhanced expression of microRNA167

et al. 2006

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ORIGINAL ARTICLEThe plant hormone auxin plays a critical role in regulating plant growth and development. Recent advances have been made in the understanding of auxin response pathways, primarily by the characterization of auxin response mutants in Arabidopsis. In addition, microRNAs (miRNAs) have been shown to be critical regulators of genes important for normal plant development and physiology. However, little is known about possible interactions between miRNAs and hormonal signaling during normal development. Here we show that an Arabidopsis microRNA, miR167, which has a complementary sequence to a portion of the AUXIN RESPONSE FACTOR6 (ARF6) and ARF8 mRNAs, can cause transcript degradation for ARF8, but not for ARF6. We report phenotypic characterizations of 35S::MIR167b transgenic lines, and show that severe 35S::MIR167b transgenic lines had phenotypes similar to those of an arf6 arf8 double mutant. The transgenic phenotypes suggest that miR167 may repress ARF6 at the level of translation. We demonstrate that the transgenic plants are defective in all four whorls of floral organs. In the transgenic flowers, filaments were abnormally short, anthers could not properly release pollen, and pollen grains did not germinate. Our results provide an important link between the miRNA-mediated regulatory pathway of gene expression and the auxin signaling network promoting plant reproductive development.Cell IntroductionThe plant hormone auxin plays a crucial role in developmental processes throughout the life cycle of a plant, including cell division and elongation, vascular tissue differentiation, root initiation, apical dominance, gravitropic and phototropic responses, fruit ripening, leaf senescence, and abscission of leaves and fruits [1]. How a simple chemical substance can affect such a wide variety of physiological processes has puzzled scientists in this field for many years. Recently, the identification of a gene family encoding proteins called auxin response factors (ARFs) in Arabidopsis [2, 3] provides a good entry to study auxin regulation at the molecular level. The ARF proteins can bind to the auxin-responsive cis elements in the promoter regions of members of an auxin-responsive gene family, GH3 [3]. The Arabidopsis genome encodes 23 known ARF proteins. Most ARF proteins contain an N-terminal domain for DNA-binding, a central region, and a C-terminal domain for protein-protein interaction [4]. ARF proteins can either activate or repress downstream genes, primarily depending on the amino acid sequence of their central region [5].Recently, miRNAs have been shown to play important roles in plant development and are widely believed to act as internal signals [6][7][8][9]. However, very little is known about the cross talk between miRNA signals and hormones. In Arabidopsis, a number of miRNAs were identified, showing critical roles in developmental regulations [7,[10][11][12][13][14][15][16][17][18][19][20].

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A Conserved microRNA Signal Specifies Leaf Polarity

Cited by 3 publications

References 76 publications

Two small regulatory RNAs establish opposing fates of a developmental axis

Two small regulatory RNAs establish opposing fates of a developmental axis

Organ Polarity in Plants Is Specified through the Opposing Activity of Two Distinct Small Regulatory RNAs

Plant fertility defects induced by the enhanced expression of microRNA167

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