Proline controls the level of polyamines in common sage plants under normal conditions and at UV-B irradiation |
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Authors: | N L Radyukina A V Shashukova S Mapelli N I Shevyakova Vl V Kuznetsov |
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Institution: | (1) Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan;(2) State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Soil Science, Nanjing, 210008, People’s Republic of China;(3) Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa 921-8836, Japan;(4) Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, 77843-3122, TX, USA |
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Abstract: | Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4–5 true leaves were treated for 12, 24, 36, or 48 h with proline added
to nutrient medium to a final concentration of 5 mM, or irradiated with UV-B light (12.3 kJ/m2 for 10 min), or subjected to combined action of these factors. In these plants, activity of proline dehydrogenase (PDH),
the content of proline, and the contents of free and conjugated polyamines were determined in the leaves and roots. It was
shown that, in control plants, the content of endogenous proline was close to zero. In the presence of proline in medium,
its total content in the roots was 9 μmol/g fr wt in 12 h of exposure, whereas in the leaves the content of proline increased
only in 24 h and achieved only 1 μmol/g fr wt. The content of free putrescine increased in the leaves and especially in the
roots after 10-min irradiation with UV-B light. The biosynthesis of putrescine was induced in the presence of proline in medium
and was observed earlier than after UV-B irradiation. UV-B irradiation affected not only the synthesis of putrescine but also
that of spermidine and spermine; it also induced accumulation of their soluble conjugates. Exogenous proline enhanced putrescine
synthesis but inhibited the formation of polyamine soluble conjugates. At combined treatment of the two factors, the content
of free putrescine in the leaves displayed a tendency to the rise and in the roots, to the decrease. At the same time, the
content of polyamine free conjugates increased in both leaves and roots. All these facts could be considered as an indirect
indication of relationship between proline and polyamine biosyntheses. We can also state that an artificially created high
proline concentration in common sage tissues characterized of its low constitutive level resulted in disturbances in the homeostasis
of low-molecular cell metabolites and induced a requirement in its restoration by diverse ways. This agrees with activation
of PDH, a key enzyme of proline degradation. Induction of polyamine biosynthesis and changes in the content of their soluble
conjugates might be one of the ways for such restoration. Under stress conditions, the high proline concentration is not toxic
for plants because polyamines and proline are the components of the plant defense system, thus weakening damaging effects
of abiotic stressors. |
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