Synthesis of alpha-glucans in fission yeast spores is carried out by three alpha-glucan synthase paralogues, Mok12p, Mok13p and Mok14p.
Fission yeast possesses a family of (1,3)-alpha-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. mok14Delta 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, beta-glucans are more abundant than alpha-glucans (55% versus 28%). In spores, the situation was the opposite, alpha-glucans accounted for 46% while beta-glucans were approximately 38% of the total polysaccharides. We found at least two types of alpha-glucan polymers, Mok12p and Mok13p, were involved in the synthesis of the greater part of alpha-glucan in the spores envelope, a polymer that is mainly digested with alpha-1,3 glucanase, while Mok14p, homologous to starch synthases, was required for the synthesis of the iodine-reactive polymer that is made of alpha-1,4 glucose residues.
García
Ignacio
I
Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca and Departamento de Microbiología y Genética, Universidad de Salamanca. Campus Miguel de Unamuno. 37007 Salamanca, Spain.
Tajadura
Virginia
V
Martín
Victoria
V
Toda
Takashi
T
Sánchez
Yolanda
Y
D000688:Amylose / Q000096:biosynthesis; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D005936:Glucans / Q000096:biosynthesis*; D005964:Glucosyltransferases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D013172:Spores, Fungal / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*
D005936:Glucans; D011108:Polymers; D000688:Amylose; D005964:Glucosyltransferases; C040232:glucan synthase