Abstract
The first part of this work consists in the identification of a prokaryotic-type bifunctional enzyme (aspartate aminotransferase, PT-AAT) in photosynthetic cells of Sorghum–sudangrass hybrid seeds Sorghum × drummondii (Nees ex Steud.) Millsp. and Chase. The results obtained show that the enzyme is constituted by a subunit of 45 kDa immunologically similar to the enzymes of C3 plants and gymnosperms. This result suggests a high degree of conservation of the PT-AAT in higher plants. To investigate whether the expression of AAT is associated with the differentiation of leaves, we analyzed the chlorophyll levels and AAT, glutamine synthetase (GS), glutamate synthase (GOGAT), isocitrate dehydrogenase (IDH), Rubisco and nitrate reductase (NR) contents in serial sections of the leaves. The chlorophyll content was high in the top sections; and then decreased toward basal sections in a continuous gradient. The Rubisco and NR contents matched the pattern of chlorophyll in the leaves with high levels in the aged section and very low levels in the basal sections. In contrast to chlorophyll, Rubisco and NR contents, GS2 and Fd-GOGAT polypeptides markedly increased from the top to the basal sections of leaves. However the patterns of AAT and IDH polypeptides did not change in different sections. In the second part of this work, to determine the relative localization of AAT, mesophyll cells (MCs) and bundle-sheath cells (BSCs) of sorghum leaves were separated by cellulase and macerase digestion. PT-AAT protein was most abundant in MC fraction than BSC fraction.
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ACKNOWLEDGMENTS
We thank Dr. Francisco M. Cánovas Ramos for antibodies and his kind permission to conduct this study in the Laboratory of Molecular Biology and Plant Biotechnology of Malaga-Spain.
We also thank all the team of the Laboratory of Molecular Biology and Plant Biotechnology of Malaga-Spain for their valuable remarks concerning this work.
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The authors declare that they have no conflict of interest. This article does not contain any studies involving animals or human participants as objects of research.
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Abbreviations: AAT—aspartate aminotransferase; BSC—bundle-sheath cells; GOGAT—glutamate synthase; GS—glutamine synthetase; IDH—isocitrate dehydrogenase; MC—mesophyll cells; NiR—nitrite reductase; NR—nitrate reductase; PT-AAT—aspartate aminotransferase type prokaryotic.
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El Omari, R., Ben Mrid, R., Bouargalne, Y. et al. Prokaryotic-Type Aspartate Aminotransferase in Sorghum Leaves: Localization, Distribution and Potential Role. Russ J Plant Physiol 67, 697–702 (2020). https://doi.org/10.1134/S1021443720040068
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DOI: https://doi.org/10.1134/S1021443720040068