Sulfur starvation in rice: the effect on photosynthesis, carbohydrate metabolism, and oxidative stress protective pathways.
Sulfur-deficient plants generate a lower yield and have a reduced nutritional value. The process of sulfur acquisition and assimilation play an integral role in plant metabolism, and response to sulfur deficiency involves a large number of plant constituents. Rice (Oryza sativa) is the second most consumed cereal grain, and the effects of sulfur deprivation in rice were analyzed by measuring changes in photosynthesis, carbohydrate metabolism, and antioxidants. The photosynthetic apparatus was severely affected under sulfur deficiency. The Chl content was reduced by 49% because of a general reduction of PSII and PSI and the associated light-harvesting antenna. The PSII efficiency was 31% lower at growth light, and the ability of PSI to photoreduce NADP+ was decreased by 61%. The Rubisco content was also significantly reduced in the sulfur-deprived plants. The imbalances between PSII and PSI, and between photosynthesis and carbon fixation led to a general over-reduction of the photosynthetic electron carriers (higher 1-q(P)). Chromatographic analysis showed that the level of monosaccharides was lower and starch content higher in the sulfur-deprived plants. In contrast, no changes in metabolite levels were found in the tricarboxylic acid or Calvin cycle. The level of the thiol-containing antioxidant, GSH, was 70% lower and the redox state was significantly more oxidized. These changes in GSH status led to an upregulation of the cytosolic isoforms of GSH reductase and monodehydroascorbate reductase. In addition, alternative antioxidants like flavonoids and anthocyanins were increased in the sulfur-deprived plants.
Lunde
Christina
C
VKR Research Centre "Pro-Active Plants", Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark. chlu@life.ku.dk
Zygadlo
Agnieszka
A
Simonsen
Henrik Toft
HT
Nielsen
Per Lassen
PL
Blennow
Andreas
A
Haldrup
Anna
A
D000975:Antioxidants / Q000378:metabolism; D050260:Carbohydrate Metabolism / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D005978:Glutathione / Q000378:metabolism; D015151:Immunoblotting; D008027:Light; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000528:radiation effects; D018384:Oxidative Stress / Q000528:radiation effects; D010641:Phenotype; D010788:Photosynthesis / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000172:deficiency* / Q000378:metabolism
D000975:Antioxidants; D005419:Flavonoids; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D013455:Sulfur; D005978:Glutathione