Flavonoids redirect PIN-mediated polar auxin fluxes during root gravitropic responses

The rate, polarity, and symmetry of the flow of the plant hormone auxin are determined by the polar cellular localization of PIN-FORMED (PIN) auxin efflux carriers. Flavonoids, a class of secondary plant metabolites, have been suspected to modulate auxin transport and tropic responses. Nevertheless, the identity of specific flavonoid compounds involved and their molecular function and targets in vivo are essentially unknown. Here we show that the root elongation zone of agravitropic pin2/eir1/wav6/agr1 has an altered pattern and amount of flavonol glycosides. Application of nanomolar concentrations of flavonols to pin2 roots is sufficient to partially restore root gravitropism. By employing a quantitative cell biological approach, we demonstrate that flavonoids partially restore the formation of lateral auxin gradients in the absence of PIN2. Chemical complementation by flavonoids correlates with an asymmetric distribution of the PIN1 protein. pin2 complementation probably does not result from inhibition of auxin efflux, as supply of the auxin transport inhibitor N-1-naphthylphthalamic acid failed to restore pin2 gravitropism. We propose that flavonoids promote asymmetric PIN shifts during gravity stimulation, thus redirecting basipetal auxin streams necessary for root bending.     

Using Stable Isotopes to Differentiate Trophic Feeding Channels within Soil Food Webs

The soil is probably the most diverse habitat there is, with organisms ranging in sizes from less than 1 μm to several metres in length. However, it is increasingly evident that we know little about the interactions occurring between these organisms, the functions that they perform as individual species, or together within their different feeding guilds. These interactions between groups of organisms and physical and chemical processes shape the soil as a habitat and influence the nature of the soil food web with consequences for the above‐ground vegetation and food web. Protists are known as one of the most abundant groups of bacterivores within the soil; however, they are also consumers of a number of other food sources. Even though they are responsible for a large proportion of the mineralisation of bacterial biomass and have a large impact on the C and N cycles within the soil they are regularly overlooked when investigating the complete soil food web. Recently, stable isotopes have been used to determine trophic interactions and here we describe how this technique has been used to highlight linkages between protists and the soil food web.     

Regulation of the Activity in the p53 Family Depends on the Organization of the Transactivation Domain

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Oxidative stress‐induced renal telomere shortening as a mechanism of cyclosporine‐induced nephrotoxicity

Due to the association of oxidative stress and telomere shortening, it was aimed in the present study to investigate the possibility whether cyclosporine‐A exerts its nephrotoxic side effects via induction of oxidative stress‐induced renal telomere shortening and senescent phenotype in renal tissues of rats. Renal oxidative stress markers, 8‐hydroxydeoxyguanosine, malondialdehyde, and protein carbonyl groups were measured by standard methods. Telomere length and telomerase activity were also evaluated in kidney tissue samples. Results showed that cyclosporine‐A treatment significantly (P < 0.05) enhanced renal malondialdehyde, 8‐hydroxydeoxyguanosine, and protein carbonyl groups levels, decreased renal telomere length, and deteriorated renal function compared with the controls. Renal telomerase activity was not affected by cyclosporine‐A. Renal telomere length could be considered as an important parameter of both oxidative stress and kidney function. Telomere shortening and accelerated kidney aging may be caused by cyclosporine‐induced oxidative stress, indicating the potential mechanism of cyclosporine‐induced nephrotoxicity.