Systemic Signaling: A Role in Propelling Crop Yield

Food security has become a topic of great concern in many countries. Global food security depends heavily on agriculture that has access to proper resources and best practices to generate higher crop yields. Crops, as with other plants, have a variety of strategies to adapt their growth to external environments and internal needs. In plants, the distal organs are interconnected through the vascular system and intricate hierarchical signaling networks, to communicate and enhance survival within fluctuating environments. Photosynthesis and carbon allocation are fundamental to crop production and agricultural outputs. Despite tremendous progress achieved by analyzing local responses to environmental cues, and bioengineering of critical enzymatic processes, little is known about the regulatory mechanisms underlying carbon assimilation, allocation, and utilization. This review provides insights into vascular-based systemic regulation of photosynthesis and resource allocation, thereby opening the way for the engineering of source and sink activities to optimize the yield performance of major crops

Data from: A cucumber protein, Phloem Phosphate Stress Repressed 1, rapidly degrades in response to a phosphate stress condition

<p>Under depleted external phosphate (Pi), many plant species adapt to this stress by initiating downstream signalling cascades. In plants, the vascular system delivers nutrients and signalling agents to control physiological and developmental processes. Currently, limited information is available regarding the direct role of phloem-borne long-distance signals in plant growth and development under Pi-stress conditions. Here, we report on the identification and characterization of a cucumber protein, <em>Cucumis sativus</em> Phloem Phosphate-Stress-Repressed 1 (CsPPSR1), whose level in the phloem translocation stream rapidly responds to imposed Pi-limiting conditions. CsPPSR1 degradation is mediated by the 26S proteasome; under Pi-sufficient conditions, CsPPSR1 is stabilized by its phosphorylation, within the sieve tube system, through the action of CsPPSR1 Kinase. Further, we discovered that CsPPSR1 Kinase was susceptible to Pi-starvation-induced degradation, in the sieve tube system. Our findings offer insight into a molecular mechanism underlying the response of phloem-borne proteins to Pi-limited stress conditions.</p><p>Funding provided by: National Science Foundation<br>Crossref Funder Registry ID: https://ror.org/021nxhr62<br>Award Number: IOS-1339128</p><p>Funding provided by: University of California General Funds*<br>Crossref Funder Registry ID: <br>Award Number: </p><p>Funding provided by: Canada Excellence Research Chair for Food Systems and Security*<br>Crossref Funder Registry ID: <br>Award Number: </p><p>Funding provided by: Global Institute for Food Security*<br>Crossref Funder Registry ID: <br>Award Number: </p><p>Funding provided by: Canada Foundation for Innovation<br>Crossref Funder Registry ID: https://ror.org/000az4664<br>Award Number: CFI#38103</p><p>Funding provided by: New Frontiers in Research Fund*<br>Crossref Funder Registry ID: <br>Award Number: NFRFE-2020-01108</p><p>In-gel kinase assays were performed as follows: Briefly, <em>E. coli</em>-purified GFP and CsPPSR1-4M8H were used as substrates. Fast protein liquid chromatography (FPLC) fractionated cucumber phloem sap proteins were separated on a substrate-containing SDS-PAGE (200 µg/ml of each substrate). Conditioned gels were incubated with 50 µM ATP and [γ32P]-ATP (20 Ci/mL) for in-gel phosphorylation. The reaction was terminated by incubating the gels with gel wash solution (5% TCA [V/V] and 1% [W/V] sodium pyrophosphate) and phosphorimaging using a Storm 860 system (GE Healthcare Lifesciences). To identify the kinase that phosphorylated CsPPSR1, named CsPPSRK, fractions with CsPPSR1-specific phosphorylation activity were separated on a 13% SDS-PAGE gel. Then the approximate 40 kDa protein band with phosphorylation activity was excised for mass spectrometry analysis. These mass spectral data were interrogated to identify sequences associated with a protein kinase of the appropriate mass.</p&gt

Plasmodesmal endoplasmic reticulum proteins regulate intercellular trafficking of cucumber mosaic virus in Arabidopsis.

Plasmodesmata (PD) are plasma membrane-lined cytoplasmic nanochannels that mediate cell-to-cell communication across the cell wall. A range of proteins are embedded in the PD plasma membrane and endoplasmic reticulum (ER), and function in regulating PD-mediated symplasmic trafficking. However, knowledge of the nature and function of the ER-embedded proteins in the intercellular movement of non-cell-autonomous proteins is limited. Here, we report the functional characterization of two ER luminal proteins, AtBiP1/2, and two ER integral membrane proteins, AtERdj2A/B, which are located within the PD. These PD proteins were identified as interacting proteins with cucumber mosaic virus (CMV) movement protein (MP) in co-immunoprecipitation studies using an Arabidopsis-derived plasmodesmal-enriched cell wall protein preparation (PECP). The AtBiP1/2 PD location was confirmed by TEM-based immunolocalization, and their AtBiP1/2 signal peptides (SPs) function in PD targeting. In vitro/in vivo pull-down assays revealed the association between AtBiP1/2 and CMV MP, mediated by AtERdj2A, through the formation of an AtBiP1/2-AtERdj2-CMV MP complex within PD. The role of this complex in CMV infection was established, as systemic infection was retarded in bip1/bip2w and erdj2b mutants. Our findings provide a model for a mechanism by which the CMV MP mediates cell-to-cell trafficking of its viral ribonucleoprotein complex

A Novel Methyltransferase Methylates Cucumber Mosaic Virus 1a Protein and Promotes Systemic Spread▿

In mammalian and yeast systems, methyltransferases have been implicated in the regulation of diverse processes, such as protein-protein interactions, protein localization, signal transduction, RNA processing, and transcription. The Cucumber mosaic virus (CMV) 1a protein is essential not only for virus replication but also for movement. Using a yeast two-hybrid system with tobacco plants, we have identified a novel gene encoding a methyltransferase that interacts with the CMV 1a protein and have designated this gene Tcoi1 (tobacco CMV 1a-interacting protein 1). Tcoi1 specifically interacted with the methyltransferase domain of CMV 1a, and the expression of Tcoi1 was increased by CMV inoculation. Biochemical studies revealed that the interaction of Tcoi1 with CMV 1a protein was direct and that Tcoi1 methylated CMV 1a protein both in vitro and in vivo. The CMV 1a binding activity of Tcoi1 is in the C-terminal domain, which shows the methyltransferase activity. The overexpression of Tcoi1 enhanced the CMV infection, while the reduced expression of Tcoi1 decreased virus infectivity. These results suggest that Tcoi1 controls the propagation of CMV through an interaction with the CMV 1a protein