Spatiotemporal imaging clarifies leaf primordium patterning.

The first step in organ morphogenesis is the subdivision of a primordium into discrete regions by patterning genes. Recently, Burian et al. used live imaging and cell-lineage tracing to illuminate early patterning events during the establishment of leaf primordium adaxial-abaxial (dorsoventral) polarity, which clarifies controversies in the field.

Upregulation of a KN1 homolog by transposon insertion promotes leafy head development in lettuce.

Leafy head is a unique type of plant architecture found in some vegetable crops, with leaves bending inward to form a compact head. The genetic and molecular mechanisms underlying leafy head in vegetables remain poorly understood. We genetically fine-mapped and cloned a major quantitative trait locus controlling heading in lettuce. The candidate gene (LsKN1) is a homolog of knotted 1 (KN1) from Zea mays Complementation and CRISPR/Cas9 knockout experiments confirmed the role of LsKN1 in heading. In heading lettuce, there is a CACTA-like transposon inserted into the first exon of LsKN1 (LsKN1▽). The transposon sequences act as a promoter rather than an enhancer and drive high expression of LsKN1▽. The enhanced expression of LsKN1▽ is necessary but not sufficient for heading in lettuce. Data from ChIP-sequencing, electrophoretic mobility shift assays, and dual luciferase assays indicate that the LsKN1▽ protein binds the promoter of LsAS1 and down-regulates its expression to alter leaf dorsoventrality. This study provides insight into plant leaf development and will be useful for studies on heading in other vegetable crops.

Expression of a conifer COBRA-like gene ClCOBL1 from Chinese fir (Cunninghamia lanceolata) alters the leaf architecture in tobacco.

The cell wall plays crucial roles in establishing the morphology of the plant cell, defence response to biotic and abiotic stresses, and mechanical properties of organs. The COBRA gene encodes a putative glycosylphosphatidylinositol (GPI)-anchored protein that possesses the ability to modulate cellulose deposition and orient cell expansion in plant cell. We reported here the functional characterization of ClCOBL1, a conifer COBRA-like gene from the differentiating xylem of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook). ClCOBL1 belonged to a woody plant-specific clade of the COBRA protein family with several conserved motifs. Expression pattern demonstrated that ClCOBL1 was constitutively expressed but with high level in cambium region. ClCOBL1 protein was mainly located in the cell wall and plasma membrane. Overexpression of ClCOBL1 in tobacco plants yielded altered leaf adaxial-abaxial patterning and short, swollen corolla tubes. The changed leaf architecture in the ClCOBL1 overexpressors was associated with the differential expression of leaf adaxial-abaxial identity genes. Our results indicated that ClCOBL1 was involved in the determination of leaf dorsoventrality and anisotropic expansion possibly by affecting the expression of adaxial and abaxial identity genes.