TY - JOUR

T1 - Effect of oxygenconcentration in intercellular pH, glucose-6-phosphate and NTP contentin rice (Oryza sativa L) and wheat (Triticum aestivum L) root tips: in vivo 31-P-NMR study

AU - Kulichikhin, Konstantin Yu.

AU - Aitio, Olli

AU - Chirkova, Tamara V.

AU - Fagerstedt, Kurt V.

PY - 2007

Y1 - 2007

N2 - Hypoxic pretreatment is known to induce anoxia tolerance in plant speciessensitive to oxygen deprivation. However, we still do not have detailed informationon changes in cytoplasmic and vacuolar pH (pHcyt and pHvac) in plantsunder low-oxygen availability (hypoxia) and under anoxia. To investigate this,we have studied the influence of hypoxia and anoxia on pHcyt and pHvac,glucose-6-phosphate (Glc-6-P) and nucleotide triphosphate (NTP) contents inrice (Oryza sativa L.) root tips in comparison with those of wheat (Triticumaestivum L.) with in vivo 31P-nuclear magnetic resonance. Both cerealsresponded to hypoxia similarly, by rapid cytoplasmic acidification (from pH7.6–7.7 to 7.1), which was followed by slow partial recovery (0.3 units after6 h). Anoxia led to a dramatic pHcyt drop in tissues of both species (from pH7.6–7.7 to less than 7.0) and partial recovery took place in rice only. In wheat,the acidification continued to pH 6.8 after 6 h of exposure. In both plants, NTPcontent followed the dynamics of pHcyt. There was a strong correlationbetween NTP content and cytoplasmic H+ activity ([H+]cyt = 10^-pHcyt) forboth hypoxic and anoxic conditions. Glc-6-P content increased in rice underanoxia and hypoxia. In wheat, Glc-6-P was not detectable under anoxia butincreased under hypoxia. In this study, rice root tips were shown to behaveas anoxia tolerant tissues. Our results suggest that the initial cytoplasmicacidification and subsequent pHcyt are differently regulated in anoxia tolerantand intolerant plants and depend on the external oxygen concentration.

AB - Hypoxic pretreatment is known to induce anoxia tolerance in plant speciessensitive to oxygen deprivation. However, we still do not have detailed informationon changes in cytoplasmic and vacuolar pH (pHcyt and pHvac) in plantsunder low-oxygen availability (hypoxia) and under anoxia. To investigate this,we have studied the influence of hypoxia and anoxia on pHcyt and pHvac,glucose-6-phosphate (Glc-6-P) and nucleotide triphosphate (NTP) contents inrice (Oryza sativa L.) root tips in comparison with those of wheat (Triticumaestivum L.) with in vivo 31P-nuclear magnetic resonance. Both cerealsresponded to hypoxia similarly, by rapid cytoplasmic acidification (from pH7.6–7.7 to 7.1), which was followed by slow partial recovery (0.3 units after6 h). Anoxia led to a dramatic pHcyt drop in tissues of both species (from pH7.6–7.7 to less than 7.0) and partial recovery took place in rice only. In wheat,the acidification continued to pH 6.8 after 6 h of exposure. In both plants, NTPcontent followed the dynamics of pHcyt. There was a strong correlationbetween NTP content and cytoplasmic H+ activity ([H+]cyt = 10^-pHcyt) forboth hypoxic and anoxic conditions. Glc-6-P content increased in rice underanoxia and hypoxia. In wheat, Glc-6-P was not detectable under anoxia butincreased under hypoxia. In this study, rice root tips were shown to behaveas anoxia tolerant tissues. Our results suggest that the initial cytoplasmicacidification and subsequent pHcyt are differently regulated in anoxia tolerantand intolerant plants and depend on the external oxygen concentration.

U2 - 10.1111/j.1399-3054.2006.00819.x

DO - 10.1111/j.1399-3054.2006.00819.x

M3 - Article

VL - 129

SP - 507

EP - 518

JO - Physiologia Plantarum

JF - Physiologia Plantarum

SN - 0031-9317

IS - 3

ER -