Synthesis of α‐glucans in fission yeast spores is carried out by three α‐glucan synthase paralogues, Mok12p, Mok13p and Mok14p

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Abstract
El pdf del artículo es la versión pre-print.-- et al.Fission yeast possesses a family of (1,3)-α-glucan synthase-related genes; one of them, mok1+/ags1+, plays an essential function in morphogenesis during vegetative growth. Here we show that three mok1+ paralogues –mok12+, mok13+ and mok14+– are required for sporulation to succeed, acting at different stages of the spore wall maturation process. Mutation of mok12+ affected the efficiency of spore formation and spore viability. Deletion of mok13+ does not affect spore viability but the spores showed reduced resistance to stress conditions. mok14Δ mutant spores failed to accumulate the amylose-like spore wall-specific polymer. mok12+, mok13+ and mok14+ expression was restricted to sporulating cells and the proteins localized to the spore envelope but with different timing. mok11+ was also induced during the sporulation process although its deletion did not show apparently a sporulation defect. In vegetative cells, β-glucans are more abundant than α-glucans (55% versus 28%). In spores, the situation was the opposite, α-glucans accounted for 46% while β-glucans were approximately 38% of the total polysaccharides. We found at least two types of α-glucan polymers, Mok12p and Mok13p, were involved in the synthesis of the greater part of α-glucan in the spores envelope, a polymer that is mainly digested with α-1,3 glucanase, while Mok14p, homologous to starch synthases, was required for the synthesis of the iodine-reactive polymer that is made of α-1,4 glucose residues.I. García was supported by a fellowship from the Junta de Castilla y León; V. Tajadura and V. Martín were supported from a fellowship granted by the MEC, Spain. This work was supported by Grants BIO2001-1663, CSI7/01 and CSI02C05.Peer Reviewe

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