Environmental stress tolerance in maize (Zea mays): role of polyamine metabolism

Maize (Zea mays L.), a major multipurpose crop for food, feed and energy is extremely susceptible to environmental perturbations and setting off the major factors for limiting maize yield. Generally, plant yields are reduced and significantly lost to adverse environments and biotic strains. To ensure the safety of living cells under unfavourable circumstances, polyamines (PAs) play an important role in regulating the response under both abiotic and biotic stresses. It is the relative abundance of higher PAs (spermidine, Spd; spermine, Spm) vis-à-vis the diamine putrescine (Put) and PA catabolism that determines the stress tolerance in plants. Climate changes and increasing demands for production of maize have made it pressing to improve the stress tolerance strategies in this plant and it is imperative to understand the role of PAs in response to various environmental perturbations. Here, we critically review and summarise the recent literature on role of PAs in conferring stress tolerance in the golden crop. The responses in terms of PA accumulation, their mechanism of action and all the recent genetic manipulation studies carried out in PA metabolism pathway, ameliorating range of abiotic and biotic stresses have been discussed. As PA metabolism under stress conditions does not operate singly within cells and is always linked to other metabolic pathways in maize, its complex connections and role as a signalling molecule have also been discussed in this review.