A mutant of Arabidopsis thaliana, fab2 in which a profound development
al phenotype, miniature growth, is caused by an increase in the level
of the membrane fatty acid, stearate has been characterized. Miniature
growth in faba results from changes in cell expansion and maturation
processes. Leaf anatomy of fab2 is characterized by cell-specific chan
ges in expansion growth, by a lack of differentiation in the cells of
the leaf blade, and by the absence of air spaces. Leaves of fab2 lack
the basipetal gradient in cellular development which is ubiquitous in
higher plants. These cellular changes occur without distorting the chr
onology of development, or destroying the biological integrity of the
organism. A second site suppressor mutation, shs, substantially restor
es both normal fatty acid composition and normal body size, causally l
inking the two phenotypes. Growth of the fab2 mutant at high temperatu
re substantially corrects the miniature phenotype without altering the
fatty acid composition, suggesting a role for membrane structure in t
he production of the aberrant morphology.