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United States Department of Agriculture

Agricultural Research Service

Research Project: POSITIONAL CLONING IN MAIZE OF GENES THAT REGULATE PLANT ARCHITECTURE

Location: Plant Gene Expression Center Albany_CA

Title: The Liguleless narrow mutation affects proximal distal signaling and leaf growth

Authors
item Moon, Jihyun -
item Candela, Hector -
item HAKE, SARAH

Research conducted cooperatively with:
item

Submitted to: Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 8, 2012
Publication Date: January 13, 2013
Citation: Moon, J., Candela, H., Hake, S.C. 2013. The Liguleless narrow mutation affects proximal distal signaling and leaf growth. Development. 140(2):405-412.

Interpretive Summary: Leaves continuously develop at the flanks of an active shoot apical meristem, where a population of pluripotent stem cells resides. Starting as a bulge on the flank of the meristem, the newly initiated leaf becomes asymmetric in several axes: adaxial-abaxial, medial-lateral, and proximal-distal. Maize serves as an excellent model system for the study of leaf development due to the well-organized pattern of division during leaf development and the distinct tissue types in the mature leaf{{379 SHARMAN,B.C. 1942; 535 Foster, T. 2009}}. We describe the characterization and cloning of the semi-dominant Liguleless narrow-Reference (Lgn-R) mutant. We mapped Lgn to a kinase and showed that the Lgn-R mutation results in decreased kinase activity and increased mRNA levels of its paralog, sister of liguleless narrow (sln). Together, these results suggest that the regulation of lgn and sln is critical for establishing positional cues that have major impacts on developmental processes.

Technical Abstract: How cells acquire competence to differentiate according to position is an essential question in developmental biology. Maize leaves provide a unique opportunity to study positional information. In the developing leaf primordium, a line is drawn across a field of seemingly identical cells. Above the line, the cells become blade, below the line the cells become sheath and at the line, the cells differentiate into the specialized tissues of ligule and auricle. We identified a new mutation, Liguleless narrow (Lgn), that affects this patterning and shows striking defects in lateral growth as well, thus linking proximal-distal patterning to medial-lateral growth. In characterizing the defect we discovered that both the auxin transport protein ZmPIN1a and the squamosa promoter-binding protein LIGULELESS1 are expressed precisely at this positionally cued line and are disrupted by Lgn. Positional cloning and a transposon-derived allele demonstrate that LGN is a kinase. These results suggest that LGN participates in setting up positional information through a signaling cascade. Interestingly, LGN has a paralog that is upregulated in the mutant, suggesting an important feedback mechanism involved in setting the positional boundary.

Last Modified: 8/19/2014
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