Tr. Warne et al., THE ANALYSIS OF GENETICALLY AND PHYSIOLOGICALLY COMPLEX TRAITS USING CERATOPTERIS - A CASE-STUDY OF NACL-TOLERANT MUTANTS, International journal of plant sciences, 156(3), 1995, pp. 374-384
Genetic and physiological complexities associated with salt tolerance
in plants have limited progress in the analysis of specific factors re
sponsible for the salt-tolerant phenotype. We have used the homosporou
s fern Ceratopteris richardii as a model plant to investigate the phys
iological basis of salinity tolerance by selecting single gene mutants
that confer tolerance in the gametophyte generation. The unique genet
ic system of homosporous ferns permits the generation of mutants in a
genetic background nearly isogenic to the wildtype, such that comparat
ive studies with the wildtype can identify specific physiological resp
onses associated with salt tolerance. One of these mutations, stl2, co
nfers a high level of tolerance to Na+ (I-50 approximate to 175 mM NaC
l) and generates a complex suite of related phenotypes. For example, i
n addition to Na+ tolerance, stl2 exhibits tolerance to Mg(2+)salts, s
ensitivity to supplemented K+, higher K+-dependent efflux of K+, alter
ed responses to Ca2+ supplementation and moderate tolerance to osmotic
stresses. Based upon its physiological attributes, we have proposed t
hat the mechanism of action for this mutation involves an enhanced inf
lux of K+ and higher selectivity for K+ over Na+ in a KC channel. The
direct and indirect consequences of this alteration can account for Na
Cl tolerance and the other phenotypes evident in stl2. The complex set
of phenotypic responses from such a single gene mutation illustrates
the potential for even more extreme pleiotropy in multigenic salt-tole
rant strains.