THE STA-1 MUTATION PREVENTS ASSEMBLY OF STARCH GRANULES IN NITROGEN-STARVED CELLS AND SERVES AS A USEFUL MORPHOLOGICAL MARKER DURING SEXUALREPRODUCTION IN CHLAMYDOMONAS-MONOICA (CHLOROPHYCEAE)

Iodine staining of clones of nitrogen-starved Chlamydomonas cells was used to screen for mutants with altered levels or altered composition of storage starch. Mutations leading to defects in quantity or morphol ogy of starch granules not only can provide information on storage sta rch biosynthesis and granule assembly but can also be used as morpholo gical markers in genetic and cell biological studies. A mutant of Chla mydomonas monoica Strehlow devoid of starch granules was obtained foll owing ultraviolet mutagenesis. Nitrogen-starved cells of the sta-1 str ain lacked pyrenoidal starch granules and granules normally associated with thylakoid membranes. The mutant phenotype was the consequence of a single Mendelian mutation that appeared to affect granule assembly rather than starch biosynthesis per se and that had no effect on veget ative growth, sexual reproduction, or zygospore viability.