Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 91 Spec No (2), 143-8

Sugar Modulation of Alpha-Amylase Genes Under Anoxia

Affiliations

Sugar Modulation of Alpha-Amylase Genes Under Anoxia

Elena Loreti et al. Ann Bot.

Abstract

Tolerance to low oxygen availability is likely to be due to the interaction of several factors. Sugar availability is one of the elements required to support anaerobic metabolism. In cereal grains the availability of soluble sugars is limited, while starch is stored in large amounts. Degradation of starch under anoxia is therefore needed to avoid sugar starvation leading to rapid cell death. The striking difference in the ability to produce alpha-amylase when comparing the anoxia-tolerant rice (Oryza sativa L.) grains with grains of other cereals is not easily explained. Rice is able to respond to gibberellins under anoxia, but the response is too slow to explain the rapid production of alpha-amylase enzyme. In the present work we demonstrated that alpha-amylase production during the first 2 d after imbibition is mostly due to the activity of the Ramy3D gene, encoding for the G and H isoforms of alpha-amylase. The induction of Ramy3D transcription is likely to result from a low sugar content in the grains incubated under anoxia. The ability of rice embryos to sense sugars under anoxia is reported.

Figures

None
Fig. 1. Effects of anoxia, gibberellic acid and glucose on Ramy1A and Ramy3D mRNA accumulation in embryoless half‐grains. A, Northern blot analysis of Ramy1A mRNA accumulation in embryoless half‐grains incubated for 2 d in presence/absence of 1 µm GA and, when used, in presence of 100 mm glucose under aerobic/anaerobic conditions. B, Northern blot analysis of Ramy3D mRNA accumulation in embryoless half‐grains incubated for 2 d in presence/absence of GA in aerobic conditions and, when used, in presence of 100 mm glucose. C, Northern blot analysis of Ramy3D mRNA accumulation in embryoless half‐grains incubated for 2 d in air or anoxia in presence/absence of 100 mm glucose.
None
Fig. 2. Effects of anoxia and glucose on Ramy1A and Ramy3D mRNA accumulation in rice embryos. A, Northern blot analysis of Ramy1A mRNA accumulation in embryos incubated for 2 d in presence/absence of 100 mm glucose under aerobic/anaerobic conditions. B, Northern blot analysis of Ramy3D mRNA accumulation in embryos incubated for 2 d in presence/absence of 100 mm glucose under aerobic/anaerobic conditions.
None
Fig. 3. Relative importance of expression of Ramy1A versus Ramy3D under aerobic and anaerobic conditions. Quantitative data (± s.e.) from replicated (n = 3) Northern blots performed as described in Figs 1 and 2 were normalized for electrophoresis loading differences on the basis of rRNA hybridization of the same blots. A relative value of 100 is assigned to the higher level of expression detected. A, Relative accumulation of Ramy1A and Ramy3D mRNAs in aerobic and anaerobic isolated embryos incubated in the presence of 1 µm GA. B, Relative accumulation of Ramy1A and Ramy3D mRNAs in aerobic and anaerobic isolated embryoless half‐grains incubated in the presence of 1 µm GA.
None
Fig. 4. Effect of glucose on the repression of RAmy3D promoter activity under aerobic and anaerobic conditions. Transformation was performed by bombardment with Ramy3D‐GUS co‐delivered with 35S‐LUC. After trasformation the embryos were subsequently incubated for 2 d on a glucose‐free medium (Control) or a medium containing glucose (10–100 mm). Data were normalized by using the 35S‐LUC construct as internal standard. Relative GUS/LUC activity is expressed as control = 100. Data are means ± s.e. (n = 3).

Similar articles

See all similar articles

Cited by 16 PubMed Central articles

See all "Cited by" articles

Publication types

Feedback