Plant salt-stress response involves complex physiological processes. Previous studies have shown that some factors promote salt tolerance only under high transpiring condition, thus mediating ...transpiration-dependent salt tolerance (TDST). However, the mechanism underlying crop TDST remains largely unknown. Here, we report that ZmSTL1 (Salt-Tolerant Locus 1) confers natural variation of TDST in maize. ZmSTL1 encodes a dirigent protein (termed ZmESBL) localized to the Casparian strip (CS) domain. Mutants lacking ZmESBL display impaired lignin deposition at endodermal CS domain which leads to a defective CS barrier. Under salt condition, mutation of ZmESBL increases the apoplastic transport of Na
across the endodermis, and then increases the root-to-shoot delivery of Na
via transpiration flow, thereby leading to a transpiration-dependent salt hypersensitivity. Moreover, we show that the ortholog of ZmESBL also mediates CS development and TDST in Arabidopsis. Our study suggests that modification of CS barrier may provide an approach for developing salt-tolerant crops.
Abstract
Sodium (Na
+
) toxicity is one of the major damages imposed on crops by saline-alkaline stress. Here we show that natural maize inbred lines display substantial variations in shoot Na
+
...contents and saline-alkaline (NaHCO
3
) tolerance, and reveal that
ZmNSA1
(
Na
+
Content under Saline-Alkaline Condition
) confers shoot Na
+
variations under NaHCO
3
condition by a genome-wide association study. Lacking of ZmNSA1 promotes shoot Na
+
homeostasis by increasing root Na
+
efflux. A naturally occurred 4-bp deletion decreases the translation efficiency of
ZmNSA1
mRNA, thus promotes Na
+
homeostasis. We further show that, under saline-alkaline condition, Ca
2+
binds to the EF-hand domain of ZmNSA1 then triggers its degradation via 26S proteasome, which in turn increases the transcripts levels of PM-H
+
-ATPases (
MHA2
and
MHA4
), and consequently enhances SOS1 Na
+
/H
+
antiporter-mediated root Na
+
efflux. Our studies reveal the mechanism of Ca
2+
-triggered saline-alkaline tolerance and provide an important gene target for breeding saline-alkaline tolerant maize varieties.
Saline-alkali stress is a widespread adversity that severely affects plant growth and productivity. Saline-alkaline soils are characterized by high salt content and high pH values, which ...simultaneously cause combined damage from osmotic stress, ionic toxicity, high pH and HCO
/CO
stress. In recent years, many determinants of salt tolerance have been identified and their regulatory mechanisms are fairly well understood. However, the mechanism by which plants respond to comprehensive saline-alkali stress remains largely unknown. This review summarizes recent advances in the physiological, biochemical and molecular mechanisms of plants tolerance to salinity or salt- alkali stress. Focused on the progress made in elucidating the regulation mechanisms adopted by plants in response to saline-alkali stress and present some new views on the understanding of plants in the face of comprehensive stress. Plants generally promote saline-alkali tolerance by maintaining pH and Na
homeostasis, while the plants responding to HCO
/CO
stress are not exactly the same as high pH stress. We proposed that pH-tolerant or sensitive plants have evolved distinct mechanisms to adapt to saline-alkaline stress. Finally, we highlight the areas that require further research to reveal the new components of saline-alkali tolerance in plants and present the current and potential application of key determinants in breed improvement and molecular breeding.
• Maize was domesticated from Balsas teosinte c. 10 000 yr ago. Previous studies have suggested that increased tolerance to environmental stress occurred during maize domestication. However, the ...underlying genetic basis remains largely unknown.
• We used a maize (W22)–teosinte recombinant inbred line (RIL) to investigate the salt wild-type tolerance aspects of maize domestication.
• We revealed that ZmHKT2 is a major QTL that regulates K⁺ homeostasis in saline soils. ZmHKT2 encodes a K⁺-preferring HKT family transporter and probably reduces shoot K⁺ content by removing K⁺ ions from root-to-shoot flowing xylem sap, ZmHKT2 deficiency increases xylem sap and shoot K⁺ concentrations, and increases salt tolerance. A coding sequence polymorphism in the ZmHKT2W22
allele (SNP389-G) confers an amino acid variant ZmHKT2 that increases xylem sap K⁺ concentration, thereby increasing shoot K⁺ content and salt tolerance. Additional analyses showed that SNP389-G first existed in teosinte (allele frequency 56% in assayed accessions), then swept through the maize population (allele frequency 98%), and that SNP389-G probably underwent positive selection during maize domestication.
• We conclude that a domestication-associated reduction in K⁺ transport activity in ZmHKT2 underlies maize shoot K⁺ content and salt tolerance, and propose that CRISPR-based editing of ZmHKT2 might provide a feasible strategy for improving maize salt tolerance.
Soil salinity is one of several major abiotic stresses that constrain maize productivity worldwide. An improved understanding of salt-tolerance mechanisms will thus enhance the breeding of ...salt-tolerant maize and boost productivity. Previous studies have indicated that the maintenance of leaf Na+ concentration is essential for maize salt tolerance, and the difference in leaf Na+ exclusion has previously been associated with variation in salt tolerance between maize varieties.
Here, we report the identification and functional characterization of a maize salt-tolerance quantitative trait locus (QTL), Zea mays Na
+
Content1 (ZmNC1), which encodes an HKT-type transporter (designated as ZmHKT1).
We show that a natural ZmHKT1 loss-of-function allele containing a retrotransposon insertion confers increased accumulation of Na+ in leaves, and salt hypersensitivity. We next show that ZmHKT1 encodes a plasma membrane-localized Na+-selective transporter, and is preferentially expressed in root stele (including the parenchyma cells surrounding the xylem vessels). We also show that loss of ZmHKT1 function increases xylem sap Na+ concentration and causes increased root-to-shoot Na+ delivery, indicating that ZmHKT1 promotes leaf Na+ exclusion and salt tolerance by withdrawing Na+ from the xylem sap.
We conclude that ZmHKT1 is a major salt-tolerance QTL and identifies an important new gene target in breeding for improved maize salt tolerance.
Excessive sodium ion (Na
) concentrations in cultivated land alter crop yield and quality worldwide. Previous studies have shown that shoot Na
exclusion is essential in most crops for salt tolerance. ...Here, we show by a genome-wide association study that Zea may L. Na
content 2 (ZmNC2), encoding the HAK family ion transporter ZmHAK4, confers the natural variation of shoot Na
exclusion and salt tolerance in maize. The ZmHAK4 locus accounts for ~11% of the shoot Na
variation, and a natural ZmHAK4-deficient allele displays a decreased ZmHAK4 expression level and an increased shoot Na
content. ZmHAK4 is preferentially expressed in the root stele and encodes a novel membrane-localized Na
-selective transporter that mediates shoot Na
exclusion, probably by retrieving Na
from xylem sap. ZmHAK4 orthologues were identified in other plant species, and the orthologues of ZmHAK4 in rice and wheat show identical expression patterns and ion transport properties, suggesting that ZmHAK4 orthologues mediate an evolutionarily conserved salt-tolerance mechanism. Finally, we show that ZmHAK4 and ZmHKT1 (a HKT1 family Na
-selective transporter) confer distinct roles in promoting shoot Na
exclusion and salt tolerance, indicating that the combination of the favourable alleles of ZmHKT1 and ZmHAK4 can facilitate the development of salt-tolerant maize varieties.
The NAC family of transcription factors (TFs) regulate plant development and abiotic stress. However, the specific function and response mechanism of NAC TFs that increase drought resistance in
...remain largely unknown. In this study, we functionally characterized a member of the PwNAC family known as
. PwNAC31 is a nuclear-localized protein with transcriptional activation activity and contains an NAC domain that shows extensive homology with ANAC072 in
. The expression level of
is significantly upregulated under drought and ABA treatments. The heterologous expression of
in
mutants enhances the seed vigor and germination rates and restores the hypersensitive phenotype of
under drought stress, accompanied by the up-regulated expression of drought-responsive genes such as
and
. Yeast two-hybrid and bimolecular fluorescence complementation assays confirmed that PwNAC31 interacts with DREB2A and ABF3 (ABSCISIC ACID-RESPONSIVE ELEMENT-BINDING FACTOR 3). Yeast one-hybrid and dual-luciferase assays showed that PwNAC31, together with its interaction protein DREB2A, directly regulated the expression of
by binding to the DRE element of the
promoter. Collectively, our study provides evidence that PwNAC31 activates
by interacting with DREB2A to enhance drought tolerance in transgenic
.
Sucrose phloem unloading plays a vital role in photoassimilate distribution and storage in sink organs such as fruits and seeds. In most plants, the phloem unloading route was reported to shift ...between an apoplasmic and a symplasmic pattern with fruit development. However, the molecular transition mechanisms of the phloem unloading pathway still remain largely unknown. In this study, we applied RNA sequencing to profile the specific gene expression patterns for sucrose unloading in
fruits in the apo- and symplasmic pathways that were discerned by CF fluoresce labelling. Several key structural genes were identified that participate in phloem unloading, such as
,
,
,
and
. In particular, the key genes controlling the process were involved in callose metabolism, which was confirmed by callose staining. Based on the co-expression network analysis with key structural genes, a number of transcription factors belonging to the MYB, C2C2, NAC, WRKY, and AP2/ERF families were identified to be candidate regulators for the operation and transition of phloem unloading. KEGG enrichment analysis showed that some important metabolism pathways such as plant hormone metabolism, starch, and sucrose metabolism altered with the change of the sugar unloading pattern. Our study provides innovative insights into the different mechanisms responsible for apo- and symplasmic phloem unloading in oil tea fruit and represents an important step towards the omics delineation of sucrose phloem unloading transition in crops.
Blueberry (Vaccinium corymbosum L.) is an important species with a high content of flavonoids in fruits. As a perennial shrub, blueberry is characterized by shallow-rooted property and susceptible to ...drought stress. MYB transcription factor was reported to be widely involved in plant response to abiotic stresses, however, the role of MYB family in blueberry responding to drought stress remains elusive. In this study, we conducted a comprehensive analysis of VcMYBs in blueberry based on the genome data under drought stress, including phylogenetic relationship, identification of differentially expressed genes (DEGs), expression profiling, conserved motifs, expression correlation and protein-protein interaction prediction, etc. The results showed that 229 non-redundant MYB sequences were identified in the blueberry genome, and divided into 23 subgroups. A total of 102 MYB DEGs with a significant response to drought stress were identified, of which 72 in leaves and 69 in roots, and 8 differential expression genes with a > 20-fold change in the level of expression. 17 DEGs had a higher expression correlation with other MYB members. The interaction partners of the key VcMYB proteins were predicted by STRING analysis and in combination with physiological and morphological observation. 10 key VcMYB genes such as VcMYB8, VcMYB102 and VcMYB228 were predicted to be probably involved in reactive oxygen species (ROS) pathway, and 7 key VcMYB genes (VcMYB41, VcMYB88 and VcMYB100, etc..) probably participated in leaf regulation under drought treatment. Our studies provide a new understanding of the regulation mechanism of VcMYB family in blueberry response to drought stress, and lay fundamental support for future studies on blueberry grown in regions with limited water supply for this crop.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
