Nucleoside Metabolism Is Induced in Common Bean During Early Seedling Development

Abstract

Nucleoside hydrolases (NSH; nucleosidases) catalyze the cleavage of nucleosides into ribose and free nucleobases. These enzymes have been postulated as key elements controlling the ratio between nucleotide salvage and degradation. Moreover, they play a pivotal role in ureidic legumes by providing the substrate for the synthesis of ureides. Furthermore, nucleotide metabolism has a crucial role during germination and early seedling development, since the developing seedlings require high amount of nucleotide simultaneously to the mobilization of nutrient in cotyledons. In this study, we have cloned two nucleosidases genes from Phaseolus vulgaris, PvNSH1 and PvNSH2, expressed them as recombinant proteins, and characterized their catalytic activities. Both enzymes showed a broad range of substrate affinity; however, PvNSH1 exhibited the highest activity with uridine, followed by xanthosine, whereas PvNSH2 hydrolyses preferentially xanthosine and shows low activity with uridine. The study of the regulation of nucleosidases during germination and early postgerminative development indicated that nucleosidases are induced in cotyledons and embryonic axes just after the radicle emergence, coincident with the induction of nucleases activity and the synthesis of ureides in the embryonic axes, with no remarkable differences in the level of expression of both nucleosidase genes. In addition, nucleosides and nucleobase levels were determined as well in cotyledons and embryonic axes. Our results suggest that PvNSH1 and PvNSH2 play an important role in the mobilization of nutrients during this crucial stage of plant development.

Dynamic changes in the levels of metabolites and endogenous hormones during the germination of Zanthoxylum nitidum (Roxb.) DC. Seeds

“… 45 In the process of seed germination, the involvement of purine metabolism in the myriad of bioenergetic processes is required for the mobilization of storage products; moreover, active nucleotide biosynthesis is needed to provide sufficient pyrimidine nucleotides to the embryos to facilitate nucleic acid synthesis. 46 In this study, we observed that some nucleotides (cytosine, CAMP, cytidine, deoxyadenosine and guanosine) involved in the purine metabolism pathway accumulated significantly during the germination of Z. Nitidum seed, consistent with the varying trend of nucleotides during seed germination of common beans, 47 castor, 48 Arabidopsis thaliana 49 and other seeds. This finding indicates that a large number of nucleotides are required for the germination of Z. nitidum seeds in addition to the mobilization of nutrients in cotyledons.…”

Root-secreted nucleosides: signaling chemoattractants of rhizosphere bacteria

“…Nucleosides have been identified as root-secreted compounds in exudates of a few plant species (Strehmel et al, 2014;Tawaraya et al, 2014;Warren, 2015;Tang et al, 2022). However, recent works, using metabolomic approach, discovered that nucleoside secretion from roots is a common phenomenon of plants (McLaughlin et al, 2023) and that profound changes in their contents occur during plant development (Delgado-Garcıá et al, 2021). Nucleosides are mainly utilized as nutrients when other carbon sources such as sugars and amino acids are exhausted.…”

“…The search for chemoreceptor ligand binding domains by Pfam 31.0 and UniProt reference proteome databases revealed only one putative nucleoside binding domain, the gate domain model, and only few nucleotides binding domains (Ortega et al, 2017). Being building blocks of nucleic acids, nucleoside secretion is energetically and nutritionally demanding especially in early development of plants (Delgado-Garcıá et al, 2021), implying that they may act as signaling molecules rather than as nutrients. Consequently, we hypothesized that root-secreted nucleosides serve as signaling molecules that play a key role in the assemblage and configuration of the rhizosphere microbiome.…”