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Predominant localization of mitochondria enriched with glycine‐decarboxylating enzymes in bundle sheath cells of Alternanthera tenella , a C 3 –C 4 intermediate species
Author(s) -
DEVI M. T.,
RAJAGOPALAN A. V.,
RAGHAVENDRA A. S.
Publication year - 1995
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1995.tb00559.x
Subject(s) - photorespiration , vascular bundle , biology , biochemistry , glycine cleavage system , serine hydroxymethyltransferase , glycine , c4 photosynthesis , enzyme , microbiology and biotechnology , serine , botany , amino acid
Mesophyll protoplasts and bundle sheath cells were prepared by enzymatic digestion of leaves of Alternanthera tenella , a C 3 ‐C 4 intermediate species. The intercellular distribution of selected photosynthetic, photorespiratory and respiratory (mitochondrial) enzymes in these meso‐phyll and bundle sheath cells was studied. The activity levels of photosynthetic enzymes such as PEP carboxylase (EC 4.1.1.31) or NAD‐malic enzyme (EC 1.1.1.39) and photorespiratory enzymes such as glycolate oxidase (EC 1.1.3.1) or NADH‐hydroxypyruvate reductase (EC 1.1.1.29) were similar in the two cell types. The activity levels of mitochondrial TCA cycle enzymes such as citrate synthase (EC 4.1.3.7) or fumarase (EC 4.2.1.2) were 2‐ to 3‐fold higher in bundle sheath cells. On the other hand, the activity levels of mitochondrial photorespiratory enzymes, namely glycine decarboxylase (EC 2.1.2.10) and serine hydroxymethyltransferase (EC 2.1.2.1), were 6‐9‐fold higher in bundle sheath cells than in mesophyll protoplasts. Such preferential localization of mitochondria enriched with the glycine‐decarboxylating system in the inner bundle sheath cells would result in efficient refixa‐tion of CO 2 from not only photorespiration but also dark respiration before its exit from the leaf. We propose that predominant localization of mitochondria specialized in glycine decarboxylation in bundle sheath cells may form the basis of reduced photorespiration in this C 3 ‐C 4 intermediate species.