Transcription factor ATML1 is needed for giant cell patterning on the Arabidopsis sepal.

Project Summary

The formation of specialized cell types and patterns during development is necessary for the proper structure and function of a tissue.  During Arabidopsis sepal development, epidermal cells transition from being morphologically equivalent to being variable in size, where certain cells become giant (i.e. approximately one-fifth the length of the sepal) while others stay small.  Giant cells form via an alternative cell cycle called endoreduplication, where a cell replicates its DNA but does not divide.  Giant cell patterning is necessary to control sepal curvature. If this pattern is altered, sepals become deformed, leaving the sexual organs exposed.

Previously, transcription factor ATML1 has been shown to influence giant cell formation on theArabidopsis sepal; plants mutant for ATML1 lack giant cells. Interestingly, ATML1 is expressed in every epidermal cell, thus why do only certain cells become giant? To investigate the role of ATML1, we analyzed a series of plants with different ATML1 levels and saw that giant cell formation is proportional to the amount of ATML1 expressed, indicating that ATML1 acts in a dosage dependent manner. To determine whether giant cells produce more ATML1, we created a mcitrine-ATML1 translational reporter to quantify ATML1 in individual cells.  We analyzed over 500 plants and found several with a rescued giant cell phenotype, suggesting that our transgene is functional and acts similarly to endogenous ATML1. Additionally, to see if ATML1’s homolog, PDF2, acts in the same giant cell pathway, we performed an epistasis analysis between PDF2 and LGO. Like ATML1, PDF2 acts upstream of LGO.

My Experience

Before starting independent lab work at school, I considered research as a means to an end.  My experience this summer has not only reinforced my growing desire to go into research, but has developed a particular interest in plant genetics and organ development.  Besides establishing a new interest, introducing me to interesting, diverse people, and bettering lab techniques, this summer internship has improved my ability to process results and contextualize experiment progressions.  I’ve gained an appreciation of “what it means to be a scientist.”  In working with my mentor and speaking with graduate students and lead researchers, I have come to understand science, at its best, is a truly collaborative effort where people teach, provide feedback, and support other members of the community.  I have certainly benefited from this collective as an intern and look forward to furthering my research skills in order to work effectively in my future research.