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Salt‐stress induced modulation of chlorophyll biosynthesis during de‐etiolation of rice seedlings
Author(s) -
Turan Satpal,
Tripathy Baishnab C.
Publication year - 2015
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.12250
Subject(s) - protochlorophyllide , protoporphyrinogen oxidase , chlorophyll , biochemistry , biosynthesis , dehydratase , chemistry , protoporphyrin ix , greening , biology , enzyme , botany , photodynamic therapy , organic chemistry , ecology
Chlorophyll biosynthesis in plants is subjected to modulation by various environmental factors. To understand the modulation of the chlorophyll (Chl) biosynthesis during greening process by salt, 100–200 m M NaCl was applied to the roots of etiolated rice seedlings 12 h prior to the transfer to light. Application of 200 m M NaCl to rice seedlings that were grown in light for further 72 h resulted in reduced dry matter production (–58%) and Chl accumulation (–66%). Ionic imbalance due to salinity stress resulted in additional downregulation (41–45%) of seedling dry weight, Chl and carotenoid contents over and above that of similar osmotic stress induced by polyethylene glycol. Downregulation of Chl biosynthesis may be attributed to decreased activities of Chl biosynthetic pathway enzymes, i.e. 5‐aminolevulinic acid (ALA) dehydratase ( EC ‐2.4.1.24), porphobilinogen deaminase ( EC ‐4.3.1.8), coproporphyrinogen III oxidase ( EC ‐1.3.3.3), protoporphyrinogen IX oxidase ( EC ‐1.3.3.4), Mg‐protoporphyrin IX chelatase ( EC ‐6.6.1.1) and protochlorophyllide oxidoreductase ( EC ‐1.3.33.1). Reduced enzymatic activities were due to downregulation of their protein abundance and/or gene expression in salt‐stressed seedlings. The extent of downregulation of ALA biosynthesis nearly matched with that of protochlorophyllide and Chl to prevent the accumulation of highly photosensitive photodynamic tetrapyrroles that generates singlet oxygen under stress conditions. Although, ALA synthesis decreased, the gene/protein expression of glutamyl‐ tRNA reductase ( EC ‐1.2.1.70) increased suggesting it may play a role in acclimation to salt stress. The similar downregulation of both early and late Chl biosynthesis intermediates in salt‐stressed seedlings suggests a regulatory network of genes involved in tetrapyrrole biosynthesis.