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Query: UMLS:C0847097 (
acidity
)
15,165
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that exploits a temporal CO
2
pump with nocturnal CO
2
uptake and concentration to reduce photorespiration, improve water-use efficiency (WUE), and optimize the adaptability of plants to hotter and drier climates. Introducing the CAM photosynthetic machinery into C
3
(or C
4
) photosynthesis plants (CAM Biodesign) represents a potentially breakthrough strategy for improving WUE while maintaining high productivity. To optimize the success of CAM Biodesign approaches, the functional analysis of individual C
4
metabolism cycle genes is necessary to identify the essential genes for robust CAM pathway introduction. Here, we isolated and analyzed the subcellular localizations of 13 enzymes and regulatory proteins of the C
4
metabolism cycle of CAM from the common ice plant in stably transformed
Arabidopsis thaliana
. Six components of the carboxylation module were analyzed including beta-carbonic anhydrase (
McBCA2
), phosphoenolpyruvate carboxylase (
McPEPC1
), phosphoenolpyruvate carboxylase kinase (
McPPCK1
), NAD-dependent malate dehydrogenase (
McNAD-
MDH1
,
McNAD-MDH2
), and NADP-dependent malate dehydrogenase (
McNADP-
MDH1
). In addition, seven components of the decarboxylation module were analyzed including NAD-dependent malic enzyme (
McNAD-ME1
,
McNAD-ME2
), NADP-dependent malic enzyme (
McNADP-ME1
,
NADP-ME2
), pyruvate, orthophosphate dikinase (
McPPDK
), pyruvate, orthophosphate dikinase-regulatory protein (
McPPDK-RP
), and phosphoenolpyruvate carboxykinase (
McPEPCK
). Ectopic overexpression of most C
4
-metabolism cycle components resulted in increased rosette diameter, leaf area, and leaf fresh weight of
A. thaliana
except for
McNADP-
MDH1
,
McPPDK-RP
, and
McPEPCK.
Overexpression of most carboxylation module components resulted in increased stomatal conductance and dawn/dusk titratable
acidity
(TA) as an indirect measure of organic acid (mainly malate) accumulation in
A. thaliana
. In contrast, overexpression of the decarboxylating malic enzymes reduced stomatal conductance and TA. This comprehensive study provides fundamental insights into the relative functional contributions of each of the individual components of the core C
4
-metabolism cycle of CAM and represents a critical first step in laying the foundation for CAM Biodesign.
...
PMID:Laying the Foundation for Crassulacean Acid Metabolism (CAM) Biodesign: Expression of the C
4
Metabolism Cycle Genes of CAM in
Arabidopsis
. 3080 70
Fruit
acidity
is an important determinant of peach organoleptic quality, but its regulatory mechanism remains elusive. Measurement of organic acids in ripe fruits of seventy-five peach cultivars revealed the predominant components malate and citrate, accompanied by quinate. Organic acid accumulation increased at early stages of fruit growth, but exhibited a more dramatic reduction in low-acid cultivar during later stages of fruit development compared to high-acid cultivars. Low-acid cultivars showed citrate degradation and less transport of malate into the vacuole due to up- and down-regulation of a GABA pathway gene GAD and a malate transporter gene ALMT9, respectively. The NAD-
MDH1
gene might control the rate-limiting step in malate synthesis, while three genes, PDK, PK, and ADH, could affect citrate synthesis through the pyruvate-to-acetyl-CoA-to-citrate pathway. Altogether, these results suggested that malate accumulation is controlled at the level of metabolism and vacuolar storage, while metabolism is crucial for citrate accumulation in peach.
...
PMID:Assessment of organic acid accumulation and its related genes in peach. 3270 62
