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Query: UMLS:C0038187 (
starvation
)
24,951
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Citrus sinensis
seedlings were irrigated with nutrient solution at a concentration of 0 (Mg-deficiency) or 2 (Mg-sufficiency) mM Mg (NO
3
)
2
for 16 weeks. Mg-deficiency-induced interveinal
chlorosis
, vein enlargement and corkiness, and alterations of gas exchange, pigments, chlorophyll a fluorescence (OJIP) transients and related parameters were observed in middle and lower leaves, especially in the latter, but not in upper leaves. Mg-deficiency might impair the whole photosynthetic electron transport, including structural damage to thylakoids, ungrouping of photosystem II (PSII), inactivation of oxygen-evolving complex (OEC) and reaction centers (RCs), increased reduction of primary quinone electron acceptor (Q
A
) and plastoquinone pool at PSII acceptor side and oxidation of PSI end-electron acceptors, thus lowering energy transfer and absorption efficiency and the transfer of electrons to the dark reactions, hence, the rate of CO
2
assimilation in Mg-deficiency middle and lower leaves. Although potassium, Mg, manganese and zinc concentration in blades displayed a significant and positive relationship with the corresponding element concentration in veins, respectively, great differences existed in Mg-deficiency-induced alterations of nutrient concentrations between leaf blades and veins. For example, Mg-deficiency increased boron level in the blades of upper leaves, decreased boron level in the blades of lower leaves, but did not affect boron level in the blades of middle leaves and veins of upper, middle and lower leaves. To conclude, Mg-deficiency-induced interveinal
chlorosis
, vein enlargement, and corkiness, and alterations to photosynthesis and related parameters increased with increasing leaf age. Mg-deficiency-induced enlargement and corkiness of veins were not caused by Mg-deficiency-induced boron-
starvation
.
...
PMID:Magnesium-Deficiency Effects on Pigments, Photosynthesis and Photosynthetic Electron Transport of Leaves, and Nutrients of Leaf Blades and Veins in
Citrus sinensis
Seedlings. 3157 29
Zinc (Zn) is an essential micronutrient for plant growth. Accordingly, Zn deficiency (-Zn) in agricultural fields is a serious problem, especially in developing regions. Autophagy, a major intracellular degradation system in eukaryotes, plays important roles in nutrient recycling under nitrogen and carbon
starvation
. However, the relationship between autophagy and deficiencies of other essential elements remains poorly understood, especially in plants. In this study, we focused on Zn due to the property that within cells most Zn is tightly bound to proteins, which can be targets of autophagy. We found that autophagy plays a critical role during -Zn in Arabidopsis (
Arabidopsis thaliana
). Autophagy-defective plants (
atg
mutants) failed to grow and developed accelerated
chlorosis
under -Zn. As expected, -Zn induced autophagy in wild-type plants, whereas in
atg
mutants, various organelle proteins accumulated to high levels. Additionally, the amount of free Zn
2+
was lower in
atg
mutants than in control plants. Interestingly, -Zn symptoms in
atg
mutants recovered under low-light, iron-limited conditions. The levels of hydroxyl radicals in chloroplasts were elevated, and the levels of superoxide were reduced in -Zn
atg
mutants. These results imply that the photosynthesis-mediated Fenton-like reaction, which is responsible for the chlorotic symptom of -Zn, is accelerated in
atg
mutants. Together, our data indicate that autophagic degradation plays important functions in maintaining Zn pools to increase Zn bioavailability and maintain reactive oxygen species homeostasis under -Zn in plants.
...
PMID:Autophagy Increases Zinc Bioavailability to Avoid Light-Mediated Reactive Oxygen Species Production under Zinc Deficiency. 3194 69
Autophagy and the ubiquitin-proteasome system are the major degradation processes for intracellular components in eukaryotes. Although ubiquitination acts as a signal inducing organelle-targeting autophagy, the interaction between ubiquitination and autophagy in chloroplast turnover has not been addressed. In this study, we found that two chloroplast-associated E3 enzymes, SUPPRESSOR OF PPI1 LOCUS1 and PLANT U-BOX4 (PUB4), are not necessary for the induction of either piecemeal autophagy of chloroplast stroma or chlorophagy of whole damaged chloroplasts in Arabidopsis (
Arabidopsis thaliana
). Double mutations of an autophagy gene and
PUB4
caused synergistic phenotypes relative to single mutations. The double mutants developed accelerated leaf
chlorosis
linked to the overaccumulation of reactive oxygen species during senescence and had reduced seed production. Biochemical detection of ubiquitinated proteins indicated that both autophagy and PUB4-associated ubiquitination contributed to protein degradation in the senescing leaves. Furthermore, the double mutants had enhanced susceptibility to carbon or nitrogen
starvation
relative to single mutants. Together, these results indicate that autophagy and chloroplast-associated E3s cooperate for protein turnover, management of reactive oxygen species accumulation, and adaptation to
starvation
.
...
PMID:Chloroplast Autophagy and Ubiquitination Combine to Manage Oxidative Damage and Starvation Responses. 3255 6
Many microorganisms produce resting cells with very low metabolic activity that allow them to survive phases of prolonged nutrient or energy stress. In cyanobacteria and some eukaryotic phytoplankton, the production of resting stages is accompanied by a loss of photosynthetic pigments, a process termed
chlorosis
. Here, we show that a
chlorosis
-like process occurs under multiple stress conditions in axenic laboratory cultures of
Prochlorococcus
, the dominant phytoplankton linage in large regions of the oligotrophic ocean and a global key player in ocean biogeochemical cycles. In
Prochlorococcus
strain MIT9313, chlorotic cells show reduced metabolic activity, measured as C and N uptake by Nanoscale secondary ion mass spectrometry (NanoSIMS). However, unlike many other cyanobacteria, chlorotic
Prochlorococcus
cells are not viable and do not regrow under axenic conditions when transferred to new media. Nevertheless, cocultures with a heterotrophic bacterium,
Alteromonas macleodii
HOT1A3, allowed
Prochlorococcus
to survive nutrient
starvation
for months. We propose that reliance on co-occurring heterotrophic bacteria, rather than the ability to survive extended
starvation
as resting cells, underlies the ecological success of
Prochlorococcus
IMPORTANCE
The ability of microorganisms to withstand long periods of nutrient
starvation
is key to their survival and success under highly fluctuating conditions that are common in nature. Therefore, one would expect this trait to be prevalent among organisms in the nutrient-poor open ocean. Here, we show that this is not the case for
Prochlorococcus
, a globally abundant and ecologically important marine cyanobacterium. Instead,
Prochlorococcus
relies on co-occurring heterotrophic bacteria to survive extended phases of nutrient and light
starvation
. Our results highlight the power of microbial interactions to drive major biogeochemical cycles in the ocean and elsewhere with consequences at the global scale.
...
PMID:
Prochlorococcus
Cells Rely on Microbial Interactions Rather than on Chlorotic Resting Stages To Survive Long-Term Nutrient Starvation. 3278 85
Non-diazotrophic cyanobacteria are unable to fix atmospheric nitrogen and rely on combined nitrogen for growth and development. In the absence of combined nitrogen sources, most non-diazotrophic cyanobacteria, e.g.,
Synechocystis
sp. PCC 6803 or
Synechococcus elongatus
PCC 7942, enter a dormant stage called
chlorosis
. The
chlorosis
process involves switching off photosynthetic activities and downregulating protein biosynthesis. Addition of a combined nitrogen source induces the regeneration of chlorotic cells in a process called resuscitation. As heavy metals are ubiquitous in the cyanobacterial biosphere, their influence on the vegetative growth of cyanobacterial cells has been extensively studied. However, the effect of heavy metal stress on chlorotic cyanobacterial cells remains elusive. To simulate the natural conditions, we investigated the effects of long-term exposure of
S. elongatus
PCC 7942 cells to both heavy metal stress and nitrogen
starvation
. We were able to show that elevated heavy metal concentrations, especially for Ni
2+
, Cd
2+
, Cu
2+
and Zn
2+
, are highly toxic to nitrogen starved cells. In particular, cells exposed to elevated concentrations of Cd
2+
or Ni
2+
were not able to properly enter
chlorosis
as they failed to degrade phycobiliproteins and chlorophyll a and remained greenish. In resuscitation assays, these cells were unable to recover from the simultaneous nitrogen
starvation
and Cd
2+
or Ni
2+
stress. The elevated toxicity of Cd
2+
or Ni
2+
presumably occurs due to their interference with the onset of
chlorosis
in nitrogen-starved cells, eventually leading to cell death.
...
PMID:Heavy Metal Stress Alters the Response of the Unicellular Cyanobacterium
Synechococcus elongatus
PCC 7942 to Nitrogen Starvation. 3317 51
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