Faculty Opinions recommendation of Control of leaf morphogenesis by microRNAs.

AbstractHeterosis is a complex phenomenon in which hybrids show better phenotypic characteristics than their parents do. Chinese cabbage (Brassica rapa L. spp. pekinensis) is a popular leafy crop species, hybrids of which are widely used in commercial production; however, the molecular basis of heterosis for biomass of Chinese cabbage is poorly understood. We characterized heterosis in a Chinese cabbage F1 hybrid cultivar and its parental lines from the seedling stage to the heading stage; marked heterosis of leaf weight and biomass yield were observed. Small RNA sequencing revealed 63 and 50 differentially expressed microRNAs (DEMs) at the seedling and early-heading stages, respectively. The expression levels of the majority of miRNA clusters in the F1 hybrid were lower than the mid-parent values (MPVs). Using degradome sequencing, we identified 1,819 miRNA target genes. Gene ontology (GO) analyses demonstrated that the target genes of the MPV-DEMs and low parental expression level dominance (ELD) miRNAs were significantly enriched in leaf morphogenesis, leaf development, and leaf shaping. Transcriptome analysis revealed that the expression levels of photosynthesis and chlorophyll synthesis-related MPV-DEGs (differentially expressed genes) were significantly different in the F1 hybrid compared to the parental lines, resulting in increased photosynthesis capacity and chlorophyll content in the former. Furthermore, expression of genes known to regulate leaf development was also observed at the seedling stage. Arabidopsis plants overexpressing BrGRF4.2 and bra-miR396 presented increased and decreased leaf sizes, respectively. These results provide new insight into the regulation of target genes and miRNA expression patterns in leaf size and heterosis for biomass of B. rapa.

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Extended expression of MaKN1 contributes to the leaf morphology in aquatic forms of Myriophyllum aquaticum

Botany ◽

10.1139/cjb-2015-0077 ◽

2015 ◽

Vol 93 (9) ◽

pp. 611-621

Author(s):

M.D. Shafiullah ◽

Christian R. Lacroix

Keyword(s):

Apical Meristem ◽

Leaf Morphology ◽

Expression Patterns ◽

Homeobox Gene ◽

Leaf Primordia ◽

Leaf Primordium ◽

Myriophyllum Aquaticum ◽

Knox Gene ◽

Leaf Morphogenesis

Myriophyllum aquaticum (Vell.) Verdc. is heterophyllous in nature with highly dissected simple leaves consisting of several lobes. KNOX (KNOTTED1-LIKE HOMEOBOX) genes are believed to have played an important role in the evolution of leaf diversity. Up-regulation of KNOX during leaf primordium initiation can lead to leaf dissection in plants with simple leaves and, if overexpressed, can produce ectopic meristems on leaves. A previous study on KNOX gene expression in the aerial form of this species showed that this gene is expressed in the shoot apical meristem (SAM), as well as in leaf primordia P0 to P8. Based on these results, it was hypothesized that the prolonged expression of the MaKN1 (Myriophyllum aquaticum Knotted1-like homeobox) gene beyond P8, might play an important role in the generation of more lobes, longer lobes, and hydathode formation in the aquatic leaves of M. aquaticum. The technique of in situ hybridization was carried out using a previously sequenced 300 bp fragment of MaKN1 to determine the expression patterns of this gene in the shoot of aquatic forms of the plant. Expression patterns of MaKN1 revealed that the SAM and leaf primordia of aquatic forms of M. aquaticum at levels P0 (youngest) to P4 were distributed throughout these structures. The level of expression of this MaKN1 gene progressively became more localized to lobes in older leaf primordia (levels P5 to P12). Previous studies of aerial forms of this plant showed MaKN1 expression until P8. Our results with aquatic forms show that the highly dissected leaf morphology in aquatic forms was the result of the prolonged expression of MaKN1 beyond P8. This resulted in the formation of elongated and slightly more numerous lobes, and hydathodes in aquatic forms. These findings support the view that KNOX genes are important developmental regulators of leaf morphogenesis and have played an important role in the evolution of leaf forms in the plant kingdom.

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Auxin/gibberellin interactions in pea leaf morphogenesis

Botanical Journal of the Linnean Society ◽

10.1111/j.1095-8339.2006.00491.x ◽

2006 ◽

Vol 150 (1) ◽

pp. 45-59 ◽

Cited By ~ 7

Author(s):

DARLEEN A. DEMASON ◽

REKHA CHAWLA

Keyword(s):

Leaf Morphogenesis

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Leaflet initiation is temporally and spatially separated in simple and complex tomato (Solanum lycopersicum) leaf mutants: a developmental analysis

Botany ◽

10.1139/b10-051 ◽

2010 ◽

Vol 88 (8) ◽

pp. 710-724 ◽

Cited By ~ 7

Author(s):

Julie Kang ◽

Neelima R. Sinha

Keyword(s):

Histological Analysis ◽

Wild Type ◽

Knox Gene ◽

Leaf Morphogenesis ◽

Multiple Factors ◽

Developmental Program ◽

Meristematic Activity ◽

Primary Leaflet ◽

Developmental Analysis ◽

Leaf Mutants

Formation of a compound leaf requires the involvement of multiple factors, including KNOX1 gene expression. To further characterize simple and complex tomato leaf mutants, we analyzed their morphology and development by assessing: leaf phenotypes, primary leaf morphogenesis, expression of the class I KNOX gene LeT6, and meristematic activity of the marginal blastozone. Mutants with alterations in lobing and (or) pinnation (decrease/increase) were analyzed. Primary leaflet initiation is delayed in mutants with decreased lobing. In contrast, leaflet initiation is advanced or similar to the wild type in mutants with deep lobes. Leaves with increased pinnation along the rachis require a protracted developmental program to form their final leaf morphology. Using a morphometric analysis, we show that leaf complexity can be quantified. The expression pattern of LeT6 correlates with histological analysis of meristematic activity of the marginal blastozone, suggesting that LeT6 may play a role, through some unknown mechanism, to regulate meristematic competence, not only in the marginal blastozone to regulate leaflet lobing, but along the entire length of the leaf to regulate pinnation in compound leaves.

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