Comparative analyses of three legume species reveals conserved and unique root extracellular proteins

Abstract

Increasing evidence suggests that root extracellular proteins are involved in interactions between roots and their soil environment. In the present study, exudates released by 6-day-old roots of the three legume species white lupin (Lupinus albus), soybean (Glycine max), and cowpea (Vigna sinensis) were collected under axenic conditions, and their constitutively secreted proteomes were analyzed. Between 42 and 93 unique root extracellular proteins with 2 or more different peptide fragments per protein were identified by LC-MS/MS. Functional annotation of these proteins classified them into 14-16 different functional categories. Among those 14 homologous proteins were identified in at least two legume species. Among the unique proteins, 58 in white lupin, 85 in soybean, and 31 in cowpea were specific for each plant species, and many of them were classified in the same functional categories. Interestingly, in contrast to soybean and cowpea, two protein bands of approximately 16 and 30 kDa were present on the SDS-PAGE gel of white lupin. The identification of these bands revealed a class III chitinase and a thaumatin-like protein. Both belong to the class of pathogenesis-related proteins. The results imply that root extracellular proteins play important roles in the cross-talk between plant roots and the rhizosphere.

Variable responses of soybean chitinases to arsenic and cadmium stress at the whole plant level

“…Four chitinolytic proteins were detected by Konotop et al (2012) (21, 5;25;30;36, 5 kDa) and by Mohammadi and Karr (2002) (90, 70, 32 and 27 kDa). In a more recent proteomic study, however, up to nine different chitinase-like peptide fragments were identified among 85 soybean root proteins (Liao et al 2012), supporting the transcriptomic data in the Phytozome. In leaves, a profile similar as in roots was detected in this study.…”

The Apoplastic Secretome of Trichoderma virens During Interaction With Maize Roots Shows an Inhibition of Plant Defence and Scavenging Oxidative Stress Secreted Proteins

“… a www.uniprot.org/uniprot/ ; b Blast2GO https://www.blast2go.com/ ; * Hypothetical secreted proteins identified by literature review: 1 Tanveer et al, 2014 ; 2 Hajirezaei et al, 2000 ; 3 Agrawal et al, 2010 ; 4 Zhang et al, 2016 ; 5 Choi et al, 2012 ; 6 Ding et al, 2012 ; 7 Fernández et al, 2012 ; 8 Schulz et al, 2016 ; 9 Liao et al, 2012 . …”

Root exudates: the hidden part of plant defense

“…Since plants that are deficient in rhizathalene A formation were more susceptible to insect herbivory, this diterpene was suggested to be part of the constitutive direct defense system of roots. It should be noted that plants secrete a wide array of other high and low molecular mass defense compounds in the absence of pathogen elicitation [6][7][8][9][10][11][12][13][14]. Hence, the rhizosphere does not simply represent the infection court on which pathogens encounter the plant, but is also a preventive microbial buffer zone that protects against infection.…”

“…Therefore, despite its minor physical fraction proteins are engaged in the binding, trapping and aggregation of pathogenic bacteria[53,64]. Moreover, secreted antimicrobial proteins can serve as a direct external defense mechanism by repelling, inhibiting or killing pathogenic microorganisms.Proteomic analysis of the root exudates of root cap and border cells confirmed that the complex mixture of approximately >100 proteins contains mostly stress and defense-related proteins, besides structural components such as actin[9,10,13,14,27,53]. Upon encountering pathogenic interactions, the protein composition alters dynamically as antimicrobial compounds (e.g.…”