Drought, salt, and temperature stress-induced metabolic rearrangements and regulatory networks

Abstract

Plants regularly face adverse growth conditions, such as drought, salinity, chilling, freezing, and high temperatures. These stresses can delay growth and development, reduce productivity, and, in extreme cases, cause plant death. Plant stress responses are dynamic and involve complex cross-talk between different regulatory levels, including adjustment of metabolism and gene expression for physiological and morphological adaptation. In this review, information about metabolic regulation in response to drought, extreme temperature, and salinity stress is summarized and the signalling events involved in mediating stress-induced metabolic changes are presented.

Fig. 1

Schematic overview of amino acid, polyamine, and glycine betaine metabolism. Plants with enhanced or reduced activity of the indicated enzymes show altered tolerance to abiotic stress. ApGSMT, Aphanothece halophytica glycine sarcosine methyl transferase (EC 2.1.1.156); ApDMT, Aphanothece halophytica dimethylglycine methyltransferase (EC 2.1.1.157); codA, choline oxidase (EC 1.1.3.17); betA, choline dehydrogenase (EC 1.1.99.1); betB, betaine aldehyde dehydrogenase (EC 1.2.1.8); GAD, glutamate decarboxylase (EC 4.1.1.15); GABA-T, 4-aminobutyrate aminotransferase (EC 2.6.1.19); SSADH, succinic semialdehyde dehydrogenase (EC 1.2.1.16); P5CS, 1-pyrroline-5-carboxylate synthetase (EC 2.7.2.11 and EC 1.2.1.41); P5CR, pyrroline-5-carboxylate reductase (EC 1.5.1.2); ProDH, proline dehydrogenase (EC 1.5.99.8), P5CDH, 1-pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12); δ-OAT, ornithine δ-aminotransferase (EC 2.6.1.13); ADC, arginine decarboxylase (EC 4.1.1.19); ODC, ornithine decarboxylase (EC 4.1.1.17); SPDS, spermidine synthase (EC 2.5.1.16); SPMS, spermine synthase (EC 2.1.5.22); PAO, polyamine oxidase (EC 1.5.3.11); DAO, diamine oxidase (EC 1.4.3.22).

Fig. 2

Schematic overview of starch, fructan, sugar, and polyol metabolism. Plants with enhanced or reduced activity of the indicated enzymes show altered tolerance to abiotic stress. SEX1, α-glucan water dikinase (EC 2.7.9.4); St. phos, starch phosphorylase (2.4.1.1); BMY, β-amylase (EC 3.2.1.2); DPE2, glucanotransferase (EC 2.4.1.25); 1-SST, sucrose:sucrose 1-fructosyltransferase (EC 2.4.1.99); 6-SFT, sucrose:fructan 6-fructosyltransferase (EC 2.4.1.10); FBF, fructan beta-fructosidase (EC 3.2.1.80); mtlD, mannitol-1-phosphate dehydrogenase (EC 1.1.1.17); S6PDH, sorbitol-6-phosphate dehydrogenase (EC 1.1.1.200); SDH, sorbitol dehydrogenase (EC 1.1.1.14); Pase, unspecific phosphatase; MIPS, inositol-1-phosphate synthase (EC 5.5.1.4); IMP, inositol-1-phosphate phosphatase (EC 3.1.3.25); IMT, inositol methyltransferase (EC 2.1.1.40); GolS, galactinol synthase (EC 2.4.1.123); RS, raffinose synthase (EC 2.4.1.82), StS, stachyose synthase (EC 2.4.1.67); TPS, trehalose-6-phosphate synthase (EC 2.4.1.15); TPP, trehalose-6-phosphate phosphatase (EC 3.1.3.12).

Fig. 3

Stress-related protein kinases mediating solute accumulation. AtSnRK2.3, AtSnRK2.4, AtSnRK2.6, CDPK6, OsCIPK03, OsCIPK12, GhMPK6, ZmMKK4, and MsK4 positively regulate tolerance to high salinity, drought, and/or cold stress. Plants over-expressing these protein kinases and/or knock-outs of these kinases have altered proline and/or sugar levels.