Diego Wengier, Bergmann Lab, MAPK connections and connectors behind cell fate transitions in Arabidopsis stomatal development. Antony Chettoor, Evans Lab, Auxin Signaling is Associated with Antipodal Cell Proliferation and Survival in Maize

Event Dates: April 11, 2014 - 4:00pm - 5:00pm

Diego Wengier Abstract

Multicellular organisms build bodies of specialized cell types and tissues by placing the appropriate cell lineage precursor in the right place and time. While animal cells can travel to their destined locations, plants cells are attached to each other their entire lives, making communication especially important to coordinate developmental processes, establish patterns and avoid neighboring cells entering erroneous or overlapping program. To this end, plant cells need to accurately communicate their identity to their neighbors and decide their fate accordingly. A growing body of evidence implicates mitogen-activated protein kinase (MAPK) signaling networks in the molecular circuitry that modulates cell fate decisions in response to extracellular cues. However, studying MAPKs in specific plant developmental programs is challenging due to both redundancy and combinatorial lethality. The stomatal lineage in the leaf epidermis provides a tractable model to investigate the MAPK circuitry behind cell fate decisions because cells produce selective and specific phenotypic responses to the activation of the MAPK signaling network. I will present how we (1) identified MAPK network configurations linked to specific cell fate transitions, (2) “rewired” the system to identify structural determinants that ensure MAPK specific signal-to-output relationships, and (3) isolated mutants in a forward genetic screen looking for components of a MKK-specific phenotypic response. 

Antony Chettoor Abstract

In angiosperms, the female gametophyte or embryo sac is comprised of four cell types: two synergids, an egg cell, a central cell, and a variable number of antipodal cells. In some species the antipodal cells degenerate soon after cellularization, so many aspects of antipodal cell function and development have been unclear. In maize and many other grasses, the antipodal cells proliferate to produce a highly distinct cluster at the chalazal end of the embryo sac that persists at the apex of the endosperm after fertilization. The antipodal cells are a site of auxin accumulation in the maize embryo sac. Analysis of different families of genes involved in auxin biosynthesis, distribution, and signaling for expression in the embryo sac demonstrates that all steps are expressed within the embryo sac. In contrast to auxin signaling, cytokinin signaling is absent in the embryo sac and instead occurs adjacent to but outside of the antipodal cells. Mutant analysis demonstrates that auxin signaling is required for proliferation and survival of antipodal cells.