128 research outputs found
The role and regulation of ABI5 (ABA-Insensitive 5) in plant development, abiotic stress responses and phytohormone crosstalk
ABA Insensitive 5 (ABI5) is a basic leucine zipper transcription factor that plays a key role in the regulation of seed germination and early seedling growth in the presence of ABA and abiotic stresses. ABI5 functions in the core ABA signaling, which is composed of PYR/PYL/RCAR receptors, PP2C phosphatases and SnRK2 kinases, through the regulation of the expression of genes that contain the ABSCISIC ACID RESPONSE ELEMENT (ABRE) motif within their promoter region. The regulated targets include stress adaptation genes, e.g., LEA proteins. However, the expression and activation of ABI5 is not only dependent on the core ABA signaling. Many transcription factors such as ABI3, ABI4, MYB7 and WRKYs play either a positive or a negative role in the regulation of ABI5 expression. Additionally, the stability and activity of ABI5 are also regulated by other proteins through post-translational modifications such as phosphorylation, ubiquitination, sumoylation and S-nitrosylation. Moreover, ABI5 also acts as an ABA and other phytohormone signaling integrator. Components of auxin, cytokinin, gibberellic acid, jasmonate and brassinosteroid signaling and metabolism pathways were shown to take part in ABI5 regulation and/or to be regulated by ABI5. Monocot orthologs of AtABI5 have been identified. Although their roles in the molecular and physiological adaptations during abiotic stress have been elucidated, knowledge about their detailed action still remains elusive. Here, we describe the recent advances in understanding the action of ABI5 in early developmental processes and the adaptation of plants to unfavorable environmental conditions. We also focus on ABI5 relation to other phytohormones in the abiotic stress response of plants
Updates on the Role of ABSCISIC ACID INSENSITIVE 5 (ABI5) and ABSCISIC ACID-RESPONSIVE ELEMENT BINDING FACTORs (ABFs) in ABA Signaling in Different Developmental Stages in Plants
The core abscisic acid (ABA) signaling pathway consists of receptors, phosphatases, kinases
and transcription factors, among them ABA INSENSITIVE 5 (ABI5) and ABRE BINDING
FACTORs/ABRE-BINDING PROTEINs (ABFs/AREBs), which belong to the BASIC LEUCINE ZIPPER
(bZIP) family and control expression of stress-responsive genes. ABI5 is mostly active in seeds
and prevents germination and post-germinative growth under unfavorable conditions. The activity
of ABI5 is controlled at transcriptional and protein levels, depending on numerous regulators, including
components of other phytohormonal pathways. ABFs/AREBs act redundantly in regulating
genes that control physiological processes in response to stress during vegetative growth. In this
review, we focus on recent reports regarding ABI5 and ABFs/AREBs functions during abiotic stress
responses, which seem to be partially overlapping and not restricted to one developmental stage in
Arabidopsis and other species. Moreover, we point out that ABI5 and ABFs/AREBs play a crucial
role in the core ABA pathway’s feedback regulation. In this review, we also discuss increased stress
tolerance of transgenic plants overexpressing genes encoding ABA-dependent bZIPs. Taken together,
we show that ABI5 and ABFs/AREBs are crucial ABA-dependent transcription factors regulating
processes essential for plant adaptation to stress at different developmental stages
Barley ABI5 (Abscisic Acid INSENSITIVE 5) Is Involved in Abscisic Acid-Dependent Drought Response
ABA INSENSITIVE 5 (ABI5) is a basic leucine zipper (bZIP) transcription factor which acts
in the abscisic acid (ABA) network and is activated in response to abiotic stresses.
However, the precise role of barley (Hordeum vulgare) ABI5 in ABA signaling and its
function under stress remains elusive. Here, we show that HvABI5 is involved in ABAdependent
regulation of barley response to drought stress. We identified barley TILLING
mutants carrying different alleles in the HvABI5 gene and we studied in detail the
physiological and molecular response to drought and ABA for one of them. The
hvabi5.d mutant, carrying G1751A transition, was insensitive to ABA during seed
germination, yet it showed the ability to store more water than its parent cv.
“Sebastian” (WT) in response to drought stress. The drought-tolerant phenotype of
hvabi5.d was associated with better membrane protection, higher flavonoid content,
and faster stomatal closure in the mutant under stress compared to the WT. The
microarray transcriptome analysis revealed up-regulation of genes associated with cell
protection mechanisms in the mutant. Furthermore, HvABI5 target genes: HVA1 and
HVA22 showed higher activity after drought, which may imply better adaptation of
hvabi5.d to stress. On the other hand, chlorophyll content in hvabi5.d was lower than
in WT, which was associated with decreased photosynthesis efficiency observed in the
mutant after drought treatment. To verify that HvABI5 acts in the ABA-dependent manner
we analyzed expression of selected genes related to ABA pathway in hvabi5.d and its WT
parent after drought and ABA treatments. The expression of key genes involved in ABA
metabolism and signaling differed in the mutant and the WT under stress. Droughtinduced
increase of expression of HvNCED1, HvBG8, HvSnRK2.1, and HvPP2C4 genes
was 2–20 times higher in hvabi5.d compared to “Sebastian”. We also observed a faster
stomatal closure in hvabi5.d and much higher induction of HvNCED1 and HvSnRK2.1
genes after ABA treatment. Together, these findings demonstrate that HvABI5 plays a role
in regulation of drought response in barley and suggest that HvABI5 might be engaged in
the fine tuning of ABA signaling by a feedback regulation between biosynthetic and
signaling events. In addition, they point to different mechanisms of HvABI5 action in
regulating drought response and seed germination in barley
Methyl Jasmonate Affects Photosynthesis Efficiency, Expression of HvTIP Genes and Nitrogen Homeostasis in Barley
Jasmonates modulate many growth and developmental processes and act as stress hormones
that play an important role in plant tolerance to biotic and abiotic stresses. Therefore, there is a
need to identify the genes that are regulated through the jasmonate signalling pathway. Aquaporins,
and among them the Tonoplast Intrinsic Proteins (TIPs), form the channels in cell membranes that
are responsible for the precise regulation of the movement of water and other substrates between
cell compartments. We identified the cis-regulatory motifs for the methyl jasmonate (MeJA)-induced
genes in the promoter regions of all the HvTIP genes, which are active in barley seedlings, and thus we
hypothesised that the HvTIP expression could be a response to jasmonate signalling. In the presented
study, we determined the e ect of methyl jasmonate on the growth parameters and photosynthesis
e ciency of barley seedlings that had been exposed to di erent doses of MeJA (15–1000 M 120 h)
in a hydroponic solution. All of the applied MeJA concentrations caused a significant reduction of
barley seedling growth, which was most evident in the length of the first leaf sheath and dry leaf
weight. The observed decrease of the PSII parameters after the exposure to high doses of MeJA
(500 M or higher) was associated with the downregulation of HvPsbR gene encoding one of the
extrinsic proteins of the Oxygen Evolving Complex. The reduced expression of HvPsbR might lead
to the impairment of the OEC action, manifested by the occurrence of the K-band in an analysis of
fluorescence kinetics after MeJA treatment as well as reduced photosynthesis e ciency. Furthermore,
methyl jasmonate treatment caused a decrease in the nitrogen content in barley leaves, which was
associated with an increased expression the four tonoplast aquaporin genes (HvTIP1;2, HvTIP2;2,
HvTIP4;1 and HvTIP4;2) predicted to transport the nitrogen compounds from the vacuole to the
cytosol. The upregulation of the nitrogen-transporting HvTIPs might suggest their involvement in
the vacuolar unloading of ammonia and urea, which both could be remobilised when the nitrogen
content in the leaves decreases. Our research provides tips on physiological role of the individual TIP
subfamily members of aquaporins under methyl jasmonate action
Transcriptome analysis reveals the role of the root hairs as environmental sensors to maintain plant functions under water-deficiency conditions
An important part of the root system is the root hairs, which play a role in mineral and water uptake. Here, we present an analysis of the transcriptomic response to water deficiency of the wild-Type (WT) barley cultivar 'Karat' and its root-hairless mutant rhl1.a. A comparison of the transcriptional changes induced by water stress resulted in the identification of genes whose expression was specifically affected in each genotype. At the onset of water stress, more genes were modulated by water shortage in the roots of the WT plants than in the roots of rhl1.a. The roots of the WT plants, but not of rhl1.a, specifically responded with the induction of genes that are related to the abscisic acid biosynthesis, stomatal closure, and cell wall biogenesis, thus indicating the specific activation of processes that are related to water-stress signalling and protection. On the other hand, the processes involved in the further response to abiotic stimuli, including hydrogen peroxide, heat, and high light intensity, were specifically up-regulated in the leaves of rhl1.a. An extended period of severe stress caused more drastic transcriptome changes in the roots and leaves of the rhl1.a mutant than in those of the WT. These results are in agreement with the much stronger damage to photosystem II in the rhl1.a mutant than in its parent cultivar after 10 d of water stress. Taking into account the putative stress sensing and signalling features of the root hair transcriptome, we discuss the role of root hairs as sensors of environmental conditions
Influence of short-term macronutrient deprivation in maize on photosynthetic characteristics, transpiration and pigment content
The aim of the research was to compare the impact of short-term deprivation of selected
macronutrients (Ca, K, Mg and P) on the photosynthetic characteristics, transpiration and pigment
content in maize. The strongest inhibition of photosynthesis was caused by a deprivation of Mg,
which was visible as a decrease in the photosynthetic and transpiration rates, stomatal conductance,
photosystem II (PSII) performance, chlorophyll and flavonol content with a simultaneously increased
content of anthocyanins. In the K-deprived plants, a decrease in the photosynthetic rate was observed.
However, the transpiration rate and stomatal conductance did not differ significantly compared with
the control. In the K-deprived plants, a decrease in chlorophyll and an increase in the anthocyanin
content were also observed. We showed that Ca starvation resulted in a decrease in the photosynthetic
and transpiration rates, stomatal conductance and PSII performance, while the pigment content was
not significantly different compared with the control. In the case of P-deprived plants, we observed
a decrease in the photosynthetic and transpiration rates. Interestingly, the inhibition of stomatal
conductance was the strongest in the P-deprived plants compared with all of the investigated elements.
However, the performance of PSII was not significantly affected by P starvation compared with the
control. Our results present for the first time a comprehensive analysis of the effect of short-term
macronutrient deprivation on photosynthesis and transpiration in maize plants
Mutation in HvCBP20 (Cap binding protein 20) adapts barley to drought stress at phenotypic and transcriptomic levels
This work was supported by the European Regional Development Fund through the Innovative Economy for Poland 2007–2013, project WND-POIG.01.03.01-00-101/08 POLAPGEN-BD “Biotechnological tools for breeding cereals with increased resistance to drought,” task 22; National Science Centre, Poland, project SONATA 2015/19/D/NZ9/03573 “Translational genomics approach to identify the mechanisms of CBP20 signalosome in Arabidopsis and barley under drought stress.”CBP20 (Cap-Binding Protein 20) encodes a small subunit of the cap-binding complex (CBC), which is involved in the conserved cell processes related to RNA metabolism in plants and, simultaneously, engaged in the signaling network of drought response, which is dependent on ABA. Here, we report the enhanced tolerance to drought stress of barley mutant in the HvCBP20 gene manifested at the morphological, physiological, and transcriptomic levels. Physiological analyses revealed differences between the hvcbp20.ab mutant and its WT in response to a water deficiency. The mutant exhibited a higher relative water content (RWC), a lower stomatal conductance and changed epidermal pattern compared to the WT after drought stress. Transcriptome analysis using the Agilent Barley Microarray integrated with observed phenotypic traits allowed to conclude that the hvcbp20.ab mutant exhibited better fitness to stress conditions by its much more efficient and earlier activation of stress-preventing mechanisms. The network hubs involved in the adjustment of hvcbp20.ab mutant to the drought conditions were proposed. These results enabled to make a significant progress in understanding the role of CBP20 in the drought stress response.European Regional Development Fund; National Science Centre, Polan
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