Aluminium Tolerance

Under acidic (pH less than 5.0) conditions, the phytotoxic aluminum cation (Al3+) is released into the soil solution where it can damage plant roots, hampering their ability to acquire water and nutrients. Over a half of the world's arable land is acidic. Consequently, soil acidity and associated aluminum toxicity poses a major limitation to agricultural production worldwide. In Australia alone, Al toxicity affects 1.5 million hectares of cropping land and causes yield losses worth around $180 million annually. A common mechanism of Al tolerance in plants is the release of Al binding organic acids such as malate and citrate from the root tips. Al tolerance genes have been shown to encode ALMT1 or MATE transporters which facilitate this organic acid release. Rye is one of the most Al tolerant of all the cultivated cereals and provides the main focus for our studies.

Effect of aluminum toxicity on tolerant and intolerant rye varieties. Aluminum mainly damages the tips of the roots. The plants were stained with a dye shortly after treating with toxic aluminum, then allowed to resume growth under non-toxic conditions. Only the tolerant plants containing the Alt4 gene resumed root growth beyond the stained region.

Objectives

  1. Isolate the genes controlling Al tolerance in rye
  2. Determine the molecular differences that make varieties tolerant or intolerant
  3. Elucidate the structure of ALMT1 proteins and understand how structure relates to function
  4. Determine if Al tolerance genes from rye can be used to engineer superior Al tolerance in wheat

Experiment Strategies

Positional cloning identified a cluster of ALMT1 genes controlling Al tolerance at the Alt4 Al tolerance locus of rye. ALMT1 expression patterns were examined by quantitative real-time PCR. A large-insert (BAC) library of an Al tolerant rye is available at ACPFG to facilitate sequencing of Alt4 locus. Function of ALMT1 genes will be explored by monitoring tolerance and organic secretion from roots of recombinant or transgenic plants, and by electrophysiology experiments in frog eggs. ALMT1 structure will be explored by modelling and analysis of purified proteins by a variety of methods.

Current research activities

  • Characterizing the activity and substrate specificity of wheat and rye ALMT1 transporters, in collaboration with Stephen Tyerman from the University of Adelaide
  • Determining the structure of ALMT1 proteins
  • Investigating the relative importance of organic acid metabolism versus transport in Al tolerance
  • Sequencing of the Alt4 locus
  • Relating gene copy number and expression levels to Al tolerance levels of rye accessions

Contacts

Dr Nick Collins    
Prof Peter Langridge    
     

Selected Publications

  • Collins NC, Shirley NJ, Saeed M, Pallotta M, Gustafson JP (2008). An ALMT1 gene cluster controlling aluminum (Aluminum) tolerance at the Alt4 locus of rye (Secale cereale L.). Genetics, 179:669-682.
  • Shi B-J, Collins NC, Miftahudin, Schnurbusch T, Langridge P and Gustafson JP (2007) Construction of a rye cv. Blanco BAC library, and progress towards cloning the rye Alt3 aluminum (aluminum) tolerance gene. Vortrage fur Pflanzenzuchtung, 71: 205-209.
  • Shi B-J, Gustafson JP, Button J, Miyazaki J, Pallotta M, Gustafson N, Zhou H, Langridge P, Collins NC (2009). Physical analysis of the complex rye (Secale cereale L.) Alt4 aluminium (aluminum) tolerance locus using a whole-genome BAC library of rye cv. Blanco. Theoretical and Applied Genetics, 119: 695-704.
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