amylomaltase, is similar to, or more severe than that of sex1
(Lu and Sharkey, 2004; Nittyla¨ et al., 2004). These mutants
accumulate less starch than sex1 or sex4, but the proteins
blocked are further downstream in the starch degradation
pathway than the GWD or phosphoglucan phosphatase.
This allows a build-up of maltose and glucose, both of
which are reducing sugars and both may be sensed by signalling
proteins (Rolland et al., 2006). The dwarf phenotype
of these downstream mutants may be more a result of
maltose and/or glucose sensing or toxicity (Stettler et al.,
2009) and less a result of absolute carbon starvation from
an impaired ability to degrade starch.