Monogenic Recessive Mutations Causing Both Late Floral Initiation and Excess Starch Accumulation in Arabidopsis.

Abstract

A recessive Arabidopsis mutation, carbohydrate accumulation mutantl (caml), which maps to position 22.8 on chromosome 3, was identified by screening leaves of ethyl methanesulfonate-mutagenized M2 plants stained with iodine for altered starch content. lncreased starch content in leaves of the c a m l mutant was observed at the onset of flowering. This mutant also had a delayed floral initiation phenotype with more rosette leaves than the parenta1 line. In addition, activities of several enzymes associated with starch metabolism were altered in the c a m l mutant. The late-flowering mutant gigantea (gi) also manifested an elevated starch leve1 in leaves. However, not all late-flowering mutants had increased leaf starch content. Double mutants c a m l a d g l (for AJP-glucose pyrophosphorylase), c a m l pgm (for -phosphoglucomutase), and g i p g m had no observable starch in leaves but showed the late-flowering phenotype, demonstrating tThat the elevated starch content is not the cause of late floral initiation. The pleiotropic effects of c a m l and gi suggest that they may play regulatory roles in starch metabolism and floral initiation. These data suggest that starch accumulation and floral initiation may share a common regulatory pathway.

Two splice variants of the IDD14 transcription factor competitively form nonfunctional heterodimers which may regulate starch metabolism

“…Starch contents were low at ZT0 and ZT24 in plants incubated at 23 °C (Fig. 5b), as has been reported previously 16,17 . Starch accumulated rapidly during the light period but degraded during the dark period.…”

Characterization of ADG1, an Arabidopsis locus encoding for ADPG pyrophosphorylase small subunit, demonstrates that the presence of the small subunit is required for large subunit stability

“…We have isolated Arabidopsis mutants affecting starch metabolism (Eimert et al, 1995). Two of them were isolated on the basis that leaves grown under continuous light did not stain blue with iodine.…”

Abiotic stress and the plant circadian clock

“…GI protein is not thought to be an enzyme directly involved in starch metabolism, but the gi mutant was found to display a starch-excess phenotype. 96 Not only does gi accumulate starch, it also has higher proportions of simple carbohydrates, 97 suggesting that a higher rate of carbon fixation must take place to sustain such a carbohydrate metabolic imbalance. The oxidative-stress resistant phenotype observed by Kurepa et al 99 was partly explained by a constitutive higher expression of ascorbate peroxidase (APX1) and Cd/Zn and Fe superoxide dismutases (CSD2 and FeSOD, respectively).…”

“…The GI locus, which encodes for a protein with uncharacterized domains, is involved in rosette development 94 and flowering time, 95 starch metabolism, 96,97 correct circadian clock function, 95,98 and resistance to oxidative stress. 99 While the role of GI in clock control and timing of flower development are starting to emerge, its role in starch accumulation and oxidative stress is still obscure.…”