Structural and functional characteristics of S-like ribonucleases from carnivorous plants
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Although the S-like ribonucleases (RNases) share sequence homology with the S-RNases involved in the self-incompatibility mechanism in plants, they are not associated with this mechanism. They usually function in stress responses in non-carnivorous plants and in carnivory in carnivorous plants. In this study, we clarified the structures of the S-like RNases of Aldrovanda vesiculosa, Nepenthes bicalcarata and Sarracenia leucophylla, and compared them with those of other plants. At ten positions, amino acid residues are conserved or almost conserved only for carnivorous plants (six in total). In contrast, two positions are specific to non-carnivorous plants. A phylogenetic analysis revealed that the S-like RNases of the carnivorous plants form a group beyond the phylogenetic relationships of the plants. We also prepared and characterized recombinant S-like RNases of Dionaea muscipula, Cephalotus follicularis, A. vesiculosa, N. bicalcarata and S. leucophylla, and RNS1 of Arabidopsis thaliana. The recombinant carnivorous plant enzymes showed optimum activities at about pH 4.0. Generally, poly(C) was digested less efficiently than poly(A), poly(I) and poly(U). The kinetic parameters of the recombinant D. muscipula enzyme (DM-I) and A. thaliana enzyme RNS1 were similar. The k cat/K m of recombinant RNS1 was the highest among the enzymes, followed closely by that of recombinant DM-I. On the other hand, the k cat/K m of the recombinant S. leucophylla enzyme was the lowest, and was ~1/30 of that for recombinant RNS1. The magnitudes of the k cat/K m values or k cat values for carnivorous plant S-like RNases seem to correlate negatively with the dependency on symbionts for prey digestion.
KeywordsDroseraceae Enzyme kinetics Nepenthaceae Phylogenetic tree Protein structure Recombinant protein
Polymerase chain reaction
This work was supported by a research grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) to T.O.
- Corbishley TP, Johnson PJ, Williams R (1984) Serum ribonuclease. In: Hans UB, Jürgen B, Marianne G (eds) Methods of enzymatic analysis, vol 4. Verlag Chemie, Weinheim, pp 134–143Google Scholar
- Hayashi T, Kobayashi D, Kariu T, Tahara M, Hada K, Kouzuma Y, Kimura M (2003) Genomic cloning of ribonucleases in Nicotiana glutinosa leaves, as induced in response to wounding or to TMV-infection, and characterization of their promoters. Biosci Biotechnol Biochem 67:2574–2583PubMedCrossRefGoogle Scholar
- Peroutka M, Adlassnig W, Lendl T, Pranic K, Lichtscheidl IK (2008) Functional biology of carnivorous plants. In: Teixeira da Silva JA (ed) Floriculture, ornamental and plant biotechnology: Advances and topical issues. Global Science Books, Isleworth, pp 266–287Google Scholar
- Sato K, Egami F (1957) Studies on ribonucleases in Takadiastase. I. J Biochem 44:753–767Google Scholar
- Stevens PF (2001 onwards). Angiosperm phylogeny website. Version 13, July 2012. http://www.mobot.org/MOBOT/research/APweb. Accessed 13 Feb 2014
- Takahashi K, Matsumoto K, Nishii W, Muramatsu M, Kubota K (2009) Comparative studies on the acid proteinase activities in the digestive fluids of Nepenthes, Cephalotus, Dionaea, and Drosera. Carniv Plant Newsl 38:75–82Google Scholar