Mutants ofArabidopsis withAltered Regulation ofStarch Degradation1

Mutants ofArabidopsis thaliana (L.) Heynh. withaltered regulation ofstarch degradation wereidentified byscreening for plants thatretained highlevels ofleaf starch after aperiod of extended darkness. Themutantphenotype wasalsoexpressed inseeds, flowers, androots, indicating that thesamepathway of starch degradation isusedinthesetissues. Inmanyrespects, thephysiological consequences ofthemutations wereequivalent totheeffects observed inpreviously characterized mutantsof Arabidopsis thatareunable tosynthesize starch. Onemutant line, whichwascharacterized indetail, hadnormallevels of activity ofthestarch degradative enzymesa-amylase, ,6-amylase, phosphorylase, D-enzyme, anddebranching enzyme. Thus, itwas notpossible toestablish abiochemical basis forthephenotype, whichwasduetoarecessive mutation ata locusdesignated sexlatposition 12.2 onchromosome 1.Thisraises thepossibility thathitherto unidentified factors, altered bythemutation, play a keyrole inregulating orcatalyzing starch degradation.