| Popis: |
The Arabidopsissensitive-to-freezing8(sfr8) mutant exhibits reduced cell wall (CW) fucose levels and compromised freezing tolerance. To examine whether CW fucosylation also affects the response to desiccation, we tested the effect of leaf excision insfr8and the allelic mutantmur1-1. Leaf water loss was strikingly higher than in the wild type in these, but not other, fucosylation mutants. We hypothesized that reduced fucosylation in guard cell (GC) walls might limit stomatal closure through altering mechanical properties. Multifrequency atomic force microscopy (AFM) measurements revealed a reduced elastic modulus (Eʹ), representing reduced stiffness, insfr8GC walls. Interestingly, however, we discovered a compensatory mechanism whereby a concomitant reduction in the storage modulus (Eʹʹ) maintained a wild-type viscoelastic time response (tau) insfr8. Stomata in intact leaf discs ofsfr8responded normally to a closure stimulus, abscisic acid, suggesting that the time response may relate more to closure properties than stiffness does.sfr8stomatal pore complexes were larger than those of the wild type, and GCs lacked a fully developed cuticular ledge, both potential contributors to the greater leaf water loss insfr8. We present data that indicate that fucosylation-dependent dimerization of the CW pectic domain rhamnogalacturonan-II may be essential for normal cuticular ledge development and leaf water retention. |
