11small This project is funded by the USDA and a Dupont-Pioneer collaborative agreement.

All plant organs derive from populations of stem cells called meristems. These stem cells have two purposes: to divide to replace  themselves, and to give rise to daughter cells, which will differentiate into lateral organs. Consequently, plant meristems must precisely control the size of the stem cell niche via a network of positive and negative feedback signals. A loss of function in a negative regulator of stem cell fate can result in an enlarged or fasciated meristem phenotype, and a dramatic alteration in the morphology of the maize ear and tassel.

Maize is an excellent genetic model system, because of a large collection of developmental mutants, and a sequenced reference genome. Our lab has undertaken a forward genetic approach to identify key regulators of stem cell homeostasis and meristem size. Two previously cloned mutants, fasicated ear2 and thick-tassel dwarf1, encode orthologs of theArabidopsis thaliana genes CLAVATA1 and CLAVATA2, indicating the well-known CLAVATA-WUSCHEL regulatory feedback loop is conserved from dicots to monocots. Work published this year has shown that natural variation in FEA2 can enhance maize seed yield traits. However, little else is known about the control of this important developmental process in maize. Recently we have discovered additional genes that control stem cell proliferation, including additional receptors, signaling molecules and transcription factors.

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Normal and fasciated ear2 inflorescences of maize.

Normal and fasciated ear2 inflorescences of maize.

Top down view of a maize ear primoridium, viewed in the scanning electron microscope.

Top down view of a maize ear primoridium, viewed in the scanning electron microscope.