H. Nonhebel Laboratory

The biochemistry of auxin metabolism and its relationship to yield of cereal crops.

Auxin was the first plant hormone to be discovered and plays a key role in yield-related aspects of plant/crop development including pollen development, grain-fill, tillering and root architecture.
However despite at least 40 years of work, knowledge of the biosynthetic pathway and identification of genes controlling auxin production is incomplete. My group is investigating auxin synthesis and its role in regulating grain-fill in developing cereal grains. Most work to date has focussed on rice
due to the availability of full genome sequence as well as cDNA clones. However we are now in a position to extend this work to wheat or sorghum.

Work carried out with previous students has measured a 200-fold increase in auxin concentration of rice grains from days 4-14 after pollination. The increase in hormone content correlated closely with the major starch deposition stage of grain development. In addition we have identified two grain-specific
auxin synthesis genes whose expression appears to be responsible for the large increase in auxin. The grain specific "YUCCA" genes were found to be co-expressed with another auxin biosynthesis gene, previously proposed to be in separate biosynthetic pathway. We are currently working on the hypothesis
that all three genes are involved in the same pathway.

Several projects are available to extend this work:

  • The role of auxin transport and catabolism in regulating cereal grain-fill.
  • Investigating the catalytic activity of YUCCA flavin monooxygenases and the relationship between YUCCA and tryptophan aminotransferase in auxin biosynthesis.
  • The relationship between auxin and glucose signalling in developing cereal grains.
  • The role of auxin and abscisic acid in mediating the response of developing grains to salt, drought and heat stress.

Students working on any of these projects will be eligible to apply for funding from GRDC


Past Projects:

  • Are aldehyde oxidases of developing cereal grains involved in synthesis of auxin, abscisic acid or both?
  • Do plants have an indole-3-pyruvate decarboxylase?
  • Characterisation of the tryptamine pathway of auxin biosynthesis in developing rice grains

Dr. Heather M. Nonhebel, hnonheb2@une.edu.au 02 6773 2083