Siderophore-Producing Rhizobacteria as a Promising Tool for Empowering Plants to Cope with Iron Limitation in Saline Soils: A Review

Abstract

In addition to draught, plants growing in arid soils face two major challenges: high salinity and iron (Fe) deficiency. Salinity attenuates growth, affects plant physiology and causes nutrient imbalance which is, in fact, one of the major consequences of saline stress. Fe is a micro-nutrient essential for plant development. It is required for several metalloenzymes involved in photosynthesis and respiration and Fe-deficiency is associated to chlorosis and low crop productivity. The role of microbial siderophores in Fe supply to plants is well documented as well as the effect of plant growth promoting rhizobacteria (PGPR) on the Page 1 of 41 http://pedosphere.issas.ac.cn Pedosphere mitigation of saline stress in crop cultures. However, the dual effect of siderophore-producing PGPR both on salt-stress and on Fe limitation is still poorly explored. This review provides a critical perspective on the combined effect of Fe limitation and soil salinization as challenges to modern agriculture and intends to summarize some indirect evidence that argue in favour of siderophore-producing PGPR as bio-fertilization agents in salinized soils. Recent developments as well as future perspectives on the use of PGPR are discussed as clues to sustainable agriculture practices, in the context of present and future climate change scenarios.

Marinobacter changyiensis, sp. nov., isolated from offshore sediment

“…The analysis showed there were some siderophore-related genes, which indicated its potential ability for ferric-specific chelation. Siderophoreexpressing bacteria may represent a promising alternative to chemical fertilizers by simultaneously tackling salt-stress effects and Fe limitation in saline soils [55]. The G+C content of the draft genome of strain CLL7-20 T was 56.2 mol%, which is similar to that of M. adhaerens M6-53 T (56.4 mol%) [22] and in the range reported for members of the genus Marinobacter, i.e.…”

Plant-Growth-Promoting Bacteria Mitigating Soil Salinity Stress in Plants

“…Halophytes use different mechanisms to adapt to salty environments [5,11,33,[35][36][37]. The basic mechanisms include sophisticated changes at physiological, molecular, and biochemical levels: (i) modulation of hormone levels together with associate enzymes [11,38]; (ii) production of solutes and osmoprotectants [11,37,39]; (iii) modulating the K + /Na + relationship at high values, as potassium is vital for stomata and enzyme functioning, regulating toxic ion accumulation and nutrient status [5,37,40]; (iv) selective intake or extrusion of ions [41]; (v) synthetizing polyamides that take part in ROS modulation [11,42]; (vi) antioxidant compound production [11,43]; (vii) regulation of salt overly sensitive (SOS) genes as a response to salinity-produced stress [37,44]; (viii) nitric oxide generation, which activates diverse gene expression and antioxidant enzymes [11,45]; (ix) changing photosynthetic activity [12,34,46]; (x) regulation of salinity tolerance gene expression [13]. The halophytes can be classified into three major groups: obligate, facultative, and habitat-indifferent.…”

Trifolium repens-Associated Bacteria as a Potential Tool to Facilitate Phytostabilization of Zinc and Lead Polluted Waste Heaps

“…Additionally, the capability of bacteria to synthesize siderophores is a highly advantageous trait, because microbes can facilitate the uptake of iron by their host. The availability of iron for the plants indeed is mostly limited [70]. Acetoine synthesis by bacteria can promote plant growth by stimulating root development and increasing the resistance of the plants against pathogens and drought stress [71].…”