@entity3649 -depleted xyloglucan is dysfunctional and leads to dwarfism in XXXX .

@entity958 @entity40395 @entity3649
Xyloglucan is a polysaccharide that has important roles in the formation and function of the walls that surround growing land plant cells. Many of these plants synthesize xyloglucan that contains @entity3649 in two different side chains (L and F), which exist in distinct molecular environments. However, little is known about the contribution of these side chains to xyloglucan function. Here, we show that @entity958 ( @entity958 ) mutants devoid of the F side chain galactosyltransferase @entity40395 ( @entity40395 ) form xyloglucan that lacks F side chains and contains much less galactosylated xylose than its wild-type counterpart. The @entity3649 -depleted xyloglucan is dysfunctional, as it leads to mutants that are dwarfed with curled rosette leaves, short petioles, and short inflorescence stems. Moreover, cell wall matrix polysaccharides, including xyloglucan and pectin, are not properly secreted and instead accumulate within intracellular aggregates. Near-normal growth is restored by generating @entity40395 mutants that produce no detectable amounts of xyloglucan. Thus, cellular processes are affected more by the presence of the dysfunctional xyloglucan than by eliminating xyloglucan altogether. To identify structural features responsible for xyloglucan dysfunction, xyloglucan structure was modified in situ by generating @entity40395 mutants that lack specific xyloglucan xylosyltransferases (XXTs) or that overexpress the XYLOGLUCAN L-SIDE CHAIN GALACTOSYLTRANSFERASE2 (XLT2) gene. Normal growth was restored in the @entity40395 -3 mutant overexpressing XLT2 and in @entity40395 -3 xxt double mutants when the dysfunctional xyloglucan was modified by doubling the amounts of galactosylated side chains. Our study assigns a role for galactosylation in normal xyloglucan function and demonstrates that altering xyloglucan side chain structure disturbs diverse cellular and physiological processes.
