The function of barren inflorescence1 and sparse inflorescence1 in maize inflorescence development

Open Access
Barazesh, Solmaz
Graduate Program:
Integrative Biosciences
Doctor of Philosophy
Document Type:
Date of Defense:
September 03, 2008
Committee Members:
  • Paula Mc Steen, Dissertation Advisor
  • Teh Hui Kao, Committee Member
  • Hong Ma, Committee Member
  • David Braun, Committee Member
  • Paula Mc Steen, Committee Chair
  • auxin
  • inflorescence development
  • Maize
  • axillary meristem
The production of inflorescence structures allows flowering plants to reproduce, and is therefore an essential stage of plant development. The branches, florets and floral organs of the inflorescence are produced by a series of axillary meristems. In this thesis, maize mutants with defects in inflorescence development are characterized to gain insight into the pathways regulating the initiation of the axillary meristems controlling inflorescence development. Previous work revealed that the plant hormone auxin plays a central role in the initiation of lateral organs and meristems. Mutants with defects in polar auxin transport, such as pinformed1 (pin1) and pinoid (pid) of Arabidopsis, fail to initiate axillary meristems during inflorescence development and as a consequence produce sterile, pin-like inflorescences. Similarly, in maize, mutants in barren inflorescence2, the co-ortholog of PID, are also defective in axillary meristem initiation, resulting in a barren inflorescence with reduced branches, spikelets and florets. In Chapter 2, we describe the classical maize mutant Barren inflorescence1 (Bif1). Similar to bif2, Bif1 mutants produced fewer branches, spikelets, florets and floral organs than normal, the result of a failure in axillary meristem initiation. Double mutants between Bif1 and bif2 displayed a synergistic phenotype, indicating that Bif1 overlaps in function with bif2, possibly encoding a regulator of auxin transport in maize. Positional cloning of Bif1 is presented in the Appendix. In Chapters 3 and 4, the characterization of a novel maize mutant, sparse inflorescence1 (spi1) is described. spi1 mutants have defects in the initiation of axillary meristems and lateral organs during vegetative and inflorescence development. spi1 has been found to encode a flavin mono-oxygenase similar to the YUCCA (YUC) enzymes of Arabidopsis, which function in local auxin biosynthesis. Analysis of the interaction between spi1 and genes regulating auxin transport indicates auxin biosynthesis and auxin transport function synergistically to regulate axillary meristem initiation. In Chapter 4, the non-autonomous effects of the spi1 mutation are described.