The plasma membrane

Plants forage soil for water and nutrients, whose distribution is patchy and often dynamic. To improve their foraging activities, plants have evolved mechanisms to modify the physicochemical properties and microbial communities of the rhizosphere, i.e. the soil compartment under the influence of the roots. This dynamic interplay in root-soil-microbiome interactions creates emerging properties that impact plant nutrition and health. As a consequence, the rhizosphere can be considered an extended root phenotype, a manifestation of the effects of plant genes on their environment inside and/or outside of the organism. Here, we review current understanding of how plants shape the rhizosphere and the benefits it confers to plant fitness. We discuss future research challenges and how applying their solutions in crops will enable us to harvest the benefits of the extended root phenotype.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/tpj.14781

An extended root phenotype : the rhizosphere, its formation and impacts on plant fitness

Plants have evolved a repertoire of strategies collectively termed the shade-avoidance syndrome to avoid shade from canopy and compete for light with their neighbors. However, the signaling mechanism governing the adaptive changes of adult plant architecture to shade is not well understood. Here, we show that in Arabidopsis, compared with the wild type, several PHYTOCHROME-INTERACTING FACTORS (PIFS) overexpressors all display constitutive shade-avoidance syndrome under normal high red to far-red light ratio conditions but are less sensitive to the simulated shade, whereas the MIR156 overexpressors exhibit an opposite phenotype. The simulated shade induces rapid accumulation of PIF proteins, reduced expression of multiple MIR156 genes, and concomitant elevated expression of the SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) family genes. Moreover, in vivo and in vitro assays indicate that PIFs bind to the promoters of several MIR156 genes directly and repress their expression. Our results establish a direct functional link between the phytochrome-PIFs and miR156-SPL regulatory modules in mediating shade-avoidance syndrome.Plants employ developmental strategies to avoid shade and compete with neighbors for light. Here, Xie et al. show that phytochrome-interacting factors, which are regulated in a light-dependent manner, directly repress MIR156 genes and promote the expression of SPL genes to enhance shade-avoidance responses.

/pdf/phytochrome-interacting-factors-directly-suppress-mir156-hlqzkz6tpy.pdf

Phytochrome-interacting factors directly suppress MIR156 expression to enhance shade-avoidance syndrome in Arabidopsis

Vegetative phase change in Arabidopsis thaliana is mediated by a decrease in the level of MIR156A and MIR156C, resulting in an increase in the expression of their targets, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes. Changes in chromatin structure are required for the downregulation of MIR156A and MIR156C, but whether chromatin structure contributes to their initial elevated expression is unknown. We found that mutations in components of the SWR1 complex (ARP6, SEF) and in genes encoding H2A.Z (HTA9 and HTA11) reduce the expression of MIR156A and MIR156C, and accelerate vegetative phase change, indicating that H2A.Z promotes juvenile vegetative identity. However, arp6 and sef did not accelerate the temporal decline in miR156, and the downregulation of MIR156A and MIR156C was not accompanied by significant change in the level of H2A.Z at these loci. We conclude that H2A.Z contributes to the high expression of MIR156A/MIR156C early in shoot development, but does not regulate the timing of vegetative phase change. Our results also suggest that H2A.Z promotes the expression of MIR156A/MIR156C by facilitating the deposition of H3K4me3, rather than by decreasing nucleosome occupancy.

/pdf/h2a-z-promotes-the-transcription-of-mir156a-and-mir156c-in-3828dlam27.pdf

H2A.Z promotes the transcription of MIR156A and MIR156C in Arabidopsis by facilitating the deposition of H3K4me3

Effect of phosphate on the adsorption of antibiotics onto iron oxide minerals: Comparison between tetracycline and ciprofloxacin.

Rhizosphere acidification is a general response to Pi deficiency, especially in dicotyledonous plants. However, the signaling pathway underlying this process is still unclear. Here, we demonstrate that miR156 is induced in the shoots and roots of wild type Arabidopsis plants during Pi starvation. The rhizosphere acidification capacity was increased in 35S:MIR156 (miR156 overexpression) plants, but was completely inhibited in 35S:MIM156 (target mimicry) plants. Both 35S:MIR156 and 35S:MIM156 plants showed altered proton efflux and H(+)-ATPase activity. In addition, significant up-regulation of H(+)-ATPase activity in 35S:MIR156 roots coupled with increased citric acid and malic acid exudates was observed. qRT-PCR results showed that most H(+)-ATPase and PPCK gene transcript levels were decreased in 35S:MIM156 plants, which may account for the decreased H(+)-ATPase activity in 35S:MIM156 plants. MiR156 also affect the root architecture system. Collectively, our results suggest that miR156 regulates the process of rhizosphere acidification in plants.

Kai Jian Lei

Papers

miR156 modulates rhizosphere acidification in response to phosphate limitation in Arabidopsis.