Conservation of the PBL-RBOH immune module in land plants

The rapid production of reactive oxygen species (ROS) is a key signaling output in plant immunity. In the angiosperm model species Arabidopsis thaliana (hereafter Arabidopsis), recognition of non- or altered-self elicitor patterns by cell-surface immune receptors activates the receptor-like cytoplasmic kinases (RLCKs) of the AVRPPHB SUSCEPTIBLE 1 (PBS1)-like (PBL) family, particularly BOTRYTIS-INDUCED KINASE1 (BIK1).$^{1}$$^{,}$$^{2}$$^{,}$$^{3}$ BIK1/PBLs in turn phosphorylate the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) to induce apoplastic ROS production.$^{4}$$^{,}$$^{5}$ PBL and RBOH functions in plant immunity have been extensively characterized in flowering plants. Much less is known about the conservation of pattern-triggered ROS signaling pathways in non-flowering plants. In this study, we show that in the liverwort Marchantia polymorpha (hereafter Marchantia), single members of the RBOH and PBL families, namely MpRBOH1 and MpPBLa, are required for chitin-induced ROS production. MpPBLa directly interacts with and phosphorylates MpRBOH1 at specific, conserved sites within its cytosolic N terminus, and this phosphorylation is essential for chitin-induced MpRBOH1-mediated ROS production. Collectively, our work reveals the functional conservation of the PBL-RBOH module that controls pattern-triggered ROS production in land plants

Conservation of the PBL-RBOH immune module in land plants

The rapid production of reactive oxygen species (ROS) is a key signaling output in plant immunity. In the angiosperm model species Arabidopsis thaliana (hereafter Arabidopsis), recognition of non- or altered-self elicitor patterns by cell-surface immune receptors activates the receptor-like cytoplasmic kinases (RLCKs) of the AVRPPHB SUSCEPTIBLE 1 (PBS1)-like (PBL) family, particularly BOTRYTIS-INDUCED KINASE1 (BIK1).1,2,3 BIK1/PBLs in turn phosphorylate the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) to induce apoplastic ROS production.4,5 PBL and RBOH functions in plant immunity have been extensively characterized in flowering plants. Much less is known about the conservation of pattern-triggered ROS signaling pathways in non-flowering plants. In this study, we show that in the liverwort Marchantia polymorpha (hereafter Marchantia), single members of the RBOH and PBL families, namely MpRBOH1 and MpPBLa, are required for chitin-induced ROS production. MpPBLa directly interacts with and phosphorylates MpRBOH1 at specific, conserved sites within its cytosolic N terminus, and this phosphorylation is essential for chitin-induced MpRBOH1-mediated ROS production. Collectively, our work reveals the functional conservation of the PBL-RBOH module that controls pattern-triggered ROS production in land plants

Soil Type Influences Rhizosphere Bacterial Community Assemblies of Pecan Plantations, a Case Study of Eastern China

The rhizosphere microbiome is closely related to forest health and productivity. However, whether soil type affects pecan (Carya illinoinensis) rhizosphere microbiomes is unclear. We aimed to explore the diversity and structural characteristics of rhizosphere bacteria associated with pecan plantations grown in three soil types (Luvisols, Cambisols, Solonchaks) in Eastern China and analyze their potential functions through high-throughput sequencing. The results showed that the diversity and community structure of rhizosphere bacteria in pecan plantations were significantly affected by soil type and the pH, available phosphorus content, electrical conductivity, soil moisture, and ammonium nitrogen contents were the main factors. At the phylum level, the rhizosphere bacterial community composition was consistent, mainly included Actinobacteria, Proteobacteria, Acidobacteria, and Chloroflexi. At the family level, the pecan plantations formed different rhizosphere enriched biomarkers due to the influence of soil type, with functional characteristics such as plant growth promotion and soil nutrient cycling. In addition, there existed low abundance core species such as Haliangiaceae, Bryobacteraceae, and Steroidobacteraceae. They played important roles in the rhizosphere environments through their functional characteristics and community linkages. Overall, this study provides a basis for the study of the rhizosphere microbiome in different soil types of pecan plantations, and plays an important role in the sustainable management of forest soil

Impacts of Cropping Systems on Aggregates Associated Organic Carbon and Nitrogen in a Semiarid Highland Agroecosystem.

The effect of cropping system on the distribution of organic carbon (OC) and nitrogen (N) in soil aggregates has not been well addressed, which is important for understanding the sequestration of OC and N in agricultural soils. We analyzed the distribution of OC and N associated with soil aggregates in three unfertilized cropping systems in a 27-year field experiment: continuously cropped alfalfa, continuously cropped wheat and a legume-grain rotation. The objectives were to understand the effect of cropping system on the distribution of OC and N in aggregates and to examine the relationships between the changes in OC and N stocks in total soils and in aggregates. The cropping systems increased the stocks of OC and N in total soils (0-40 cm) at mean rates of 15.6 g OC m-2 yr-1 and 1.2 g N m-2 yr-1 relative to a fallow control. The continuous cropping of alfalfa produced the largest increases at the 0-20 cm depth. The OC and N stocks in total soils were significantly correlated with the changes in the >0.053 mm aggregates. 27-year of cropping increased OC stocks in the >0.053 mm size class of aggregates and N stocks in the >0.25 mm size class but decreased OC stocks in the 0.25 mm aggregate size class accounted for more than 97% of the total increases in the continuous wheat and the legume-grain rotation systems. These results suggested that long-term cropping has the potential to sequester OC and N in soils and that the increases in soil OC and N stocks were mainly due to increases associated with aggregates >0.053 mm

The effects of cropping systems on soil bulk density at the 0–20 and 20–40 cm depths.

<p>FA: Fallow treatment, CA: Continuously cropped alfalfa system; CW: continuously cropped winter wheat system; LG: Legume-grain rotation system.</p

Analysis of variance results for all the variables.

<p>Analysis of variance results for all the variables.</p

The effects of cropping systems on OC and N stocks and C/N ratios in aggregate size classes at the 0–20 and 20–40 cm depths.

<p>FA: Fallow treatment, CA: Continuously cropped alfalfa system; CW: continuously cropped winter wheat system; LG: Legume-grain rotation system.</p

The relationships between changes in OC and N stocks in total soils and changes in OC and N stocks in aggregate size classes.

<p>The units for the changes in OC and N stocks in both total soils and aggregates are kg m^-2.</p