Trophic status of Chlamydomonas reinhardtii influences the impact of iron deficiency on photosynthesis

To investigate the impact of iron deficiency on bioenergetic pathways in Chlamydomonas, we compared growth rates, iron content, and photosynthetic parameters systematically in acetate versus CO2-grown cells. Acetate-grown cells have, predictably (2-fold) greater abundance of respiration components but also, counter-intuitively, more chlorophyll on a per cell basis. We found that phototrophic cells are less impacted by iron deficiency and this correlates with their higher iron content on a per cell basis, suggesting a greater capacity/ability for iron assimilation in this metabolic state. Phototrophic cells maintain both photosynthetic and respiratory function and their associated Fe-containing proteins in conditions where heterotrophic cells lose photosynthetic capacity and have reduced oxygen evolution activity. Maintenance of NPQ capacity might contribute to protection of the photosynthetic apparatus in iron-limited phototrophic cells. Acetate-grown iron-limited cells maintain high growth rates by suppressing photosynthesis but increasing instead respiration. These cells are also able to maintain a reduced plastoquinone pool

Functional abilities of cultivable plant growth promoting bacteria associated with wheat (Triticum aestivum L.) crops

Abstract In the pursuit of sustainable agriculture, bioinoculants usage as providers of a crop's needs is a method to limit environmental damage. In this study, a collection of cultivable putative plant growth promoting (PGP) bacteria associated with wheat crops was obtained and this bacterial sample was characterized in relation to the functional diversity of certain PGP features. The isolates were obtained through classical cultivation methods, identified by partial 16S rRNA gene sequencing and characterized for PGP traits of interest. Functional diversity characterization was performed using Categorical Principal Component Analysis (CatPCA) and Multiple Correspondence Analysis (MCA). The most abundant genera found among the 346 isolates were Pseudomonas, Burkholderia, and Enterobacter. Occurrence of PGP traits was affected by genus, niche, and sampling site. A large number of genera grouped together with the ability to produce indolic compounds; phosphate solubilization and siderophores production formed a second group related to fewer genera, in which the genus Burkholderia has a great importance. The results obtained may help future studies aiming prospection of putative plant growth promoting bacteria regarding the desired organism and PGP trait

Oxidative damage and photosynthetic impairment in tropical rice cultivars upon exposure to excess iron

ABSTRACT Iron plays a pivotal role in the redox reactions of photosynthesis and metabolic processes such as chlorophyll synthesis. Iron availability in waterlogged soils can reach toxic levels and promote oxidative stress. Fe toxicity is the most concerning of stresses for rice in many lowland environments around the world and may cause severe impairments in rice photosynthesis. This study aimed to investigate the extension of oxidative stress after excess Fe exposure and its effects on the photosynthesis of rice cultivars with differential sensitivity. Three Brazilian rice cultivars (EPAGRI 107, BRSMG SELETA and BR IRGA 409) were grown in Hoagland nutrient solution (pH 4.0) with two Fe-EDTA doses corresponding to excess Fe (7 mM) and control (0.009 mM) treatments. After just three days of excess Fe exposure, there was a significant increase in iron concentration in the shoots. The BR IRGA 409 cultivar exhibited higher Fe accumulation in its shoots, and the EPAGRI 107 cultivar recorded the lowest values, which were below the critical toxicity level, as a resistance strategy. Impairment in light energy partitioning and oxidative damage became evident before changes in stomatal resistance, chlorophyll content, maximal PSII quantum yield or visual symptoms for the most sensitive cultivar (BR IRGA 409). The photosynthesis limitations, in addition to the impairment of excess energy dissipation in rice from iron toxicity, are the results of oxidative damage

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference