Abstract
BackgroundAbiotic stress causes disturbances in the cellular homeostasis. Re-adjustment of balance in carbon, nitrogen and phosphorus metabolism therefore plays a central role in stress adaptation. However, it is currently unknown which parts of the primary cell metabolism follow common patterns under different stress conditions and which represent specific responses.ResultsTo address these questions, changes in transcriptome, metabolome and ionome were analyzed in maize source leaves from plants suffering low temperature, low nitrogen (N) and low phosphorus (P) stress. The selection of maize as study object provided data directly from an important crop species and the so far underexplored C4 metabolism. Growth retardation was comparable under all tested stress conditions. The only primary metabolic pathway responding similar to all stresses was nitrate assimilation, which was down-regulated. The largest group of commonly regulated transcripts followed the expression pattern: down under low temperature and low N, but up under low P. Several members of this transcript cluster could be connected to P metabolism and correlated negatively to different phosphate concentration in the leaf tissue. Accumulation of starch under low temperature and low N stress, but decrease in starch levels under low P conditions indicated that only low P treated leaves suffered carbon starvation.ConclusionsMaize employs very different strategies to manage N and P metabolism under stress. While nitrate assimilation was regulated depending on demand by growth processes, phosphate concentrations changed depending on availability, thus building up reserves under excess conditions. Carbon and energy metabolism of the C4 maize leaves were particularly sensitive to P starvation.
Highlights
Abiotic stress causes disturbances in the cellular homeostasis
It had been shown in previous experiments, that growth stage and leaf series had significant influence on the transcriptome and metabolome profiles of maize seedlings, treatment specific changes differed thereby primarily in the amplitude of the change and not in the direction of the change [26]
A metabolic shift towards secondary metabolites was observed under P starvation conditions (Figure 3), but in contrast to low N stress, amino acids accumulated under low P conditions while phosphorylated intermediates decreased (Figure 3; [13,42])
Summary
Abiotic stress causes disturbances in the cellular homeostasis. Re-adjustment of balance in carbon, nitrogen and phosphorus metabolism plays a central role in stress adaptation. It is currently unknown which parts of the primary cell metabolism follow common patterns under different stress conditions and which represent specific responses. Depending on the nature of the stress, different parts of metabolism are affected, and adaptation to the stress requires readjustment of homeostasis on molecular, cellular and whole plant level [2]. Elucidation of the different interacting mechanisms underlying the complex plant stress response is of great general interest [4], and precondition for the improvements of crops and agricultural practices
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