Location: Plant, Soil and Nutrition ResearchTitle: Regulatory modules controlling maize inflorescence architecture) Author
Submitted to: Genome Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/27/2013
Publication Date: 12/4/2013
Citation: Eveland, A.L., Goldschmidt, A., Pautler, M., Morohashi, K., Liseron-Monfils, C., Lewis, M.W., Kumari, S., Yang, F., Hiraga, S., Unger-Wallace, E., Olson, A., Stanfield, S., Hake, S.C., Schmidt, R.J., Vollbrecht, E., Grotewold, E., Ware, D., Jackson, D. 2013. Regulatory modules controlling maize inflorescence architecture. Genome Research. 24:431-443. Interpretive Summary: Remarkable architectural diversity exists among plant inflorescences, the structures that bear flowers and ultimately the fruits and grains that we eat. Central to this variation are unique branching patterns, which shape inflorescences of crops, contributing to desirable agronomic traits such as grain yield, harvesting ability, and hybrid seed production. Among grass species, inflorescence architectures are diverse yet characterized by variations of a common, grass-specific morphology, where flowers are borne on specialized short branches called spikelets. In maize (Zea mays), these spikelets are paired, a feature unique to inflorescences of the tribe Andropogoneae, which includes other important cereal and bio-energy crops. While classical genetics experiments have identified key genes that regulate maize inflorescence architecture, relatively little is known about the molecular mechanisms and gene regulatory networks by which they modulate this grass-specific morphology. In this work we analyzed global changes in gene expression during specific developmental transitions in very young maize inflorescences. We also compared these expression changes in plants where specific genes known to be important in inflorescence branching were disrupted. This allowed us to define additional genes and pathways involved in inflorescence architecture and together with identification of genes targeted by a major regulator of branching, resolve regulatory networks. Results from this study provide a rich resource for studying many aspects of grass inflorescence evolution and development, predictive modeling of crop improvement, and translation to other cereal crops bearing grain on panicles or spikes.
Technical Abstract: Genetic control of branching is a primary determinant of yield, regulating seed number and harvesting ability, yet little is known about the molecular networks that shape grain-bearing inflorescences of cereal crops. Here, we used the maize (Zea mays) inflorescence to investigate gene networks that modulate determinacy, specifically the decision to branch. We characterized developmental transitions at the molecular level by associating spatiotemporal expression profiles with morphological changes resulting from genetic perturbations that disrupt steps in a pathway controlling branching. Developmental dynamics of genes targeted in vivo by the transcription factor RAMOSA1, a key regulator of determinacy, revealed potential mechanisms for repressing branches in distinct stem cell populations, including interactions with KNOTTED1, a master regulator of stem cell maintenance. Our results uncovered discrete developmental modules that function in determining grass-specific morphology and provide a basis for targeted crop improvement and translation to other cereal crops with comparable inflorescence architectures.