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Molecular Physiology


The importance of transporters for compatible solutes (ProTs) and GABA (GATs) for plant growth and under stress conditions

Transport is a highly dynamic process that is regulated by endogenous and environmental signals. Situations such as wounding, infection, water deficit (e.g. salinity, drought, freezing) or senescence affect long distance transport and result in massive changes in partitioning of carbon and nitrogen. During such stresses, especially during water deficit conditions, many plants accumulate osmotically active compounds such as sugars, betaines and proline, which serve several protective roles. In the specific case of proline, accumulation is achieved by up-regulating enzymes involved in its biosynthesis and by down-regulating those involved in degradation. In contrast to these metabolic events, the regulation of proline transport under stress conditions is still poorly understood. We isolated proline transporters (ProT) by heterologous complementation  of yeast mutants (Rentsch  et al., 1996). Of the proteinogenic amino acids only proline is transported by members of this family. In addition to proline, the ProTs mediate transport of the compatible solute glycine betaine and the stress-related compound 4-aminobutyric acid (GABA) (Breitkreuz  et al., 1999; Schwacke et  al., 1999, Grallath et al., 2005). Additionally, a high affinity GABA transporter (AtGAT1) was identified, that does not transport proline or glycine betaine (Meyer et al., 2006). Expression of the ProT-genes correlates with high proline content e.g. under water stress and in pollen (Rentsch et al., 1996, Schwacke et al., 1999). Nevertheless, the physiological role of transporters is still largely unclear. We are currently analyzing mutant and transgenic Arabidopsis plants with altered expression of proline and GABA permeases and altered proline metabolism to investigate the physiological significance of the transporters in more detail.



Doris Rentsch

Silke Lehmann
Stefan Meier


  • Andreas Meyer
  • Christophe Gumy
  • Luzia Guyer
  • Silke Grallath
  • Thilo Weimar
 In situ hybridization