OsHAK1

| Categories genes  | Tags vascular bundle  root  growth  shoot  salt  salt tolerance  salt stress  tolerance  stress  transporter  biomass  shoot apical meristem  potassium  steles  seedlings  drought  vegetative  drought tolerance  reproductive  homeostasis  breeding  drought stress  drought stress  stress response  leaf  salinity  pollen  panicle  phloem  fertility  plasma membrane  sugar  phosphate  sucrose  sucrose transporter 
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  • Key message
    • Expression of OsHAK1 is up-regulated by K deficiency or salt stress in various tissues, particularly in the root and shoot apical meristem, the epidermises and steles of root, and vascular bundles of shoot
    • Both oshak1 knockout mutants in comparison to their respective Dongjin or Manan wild types showed dramatically reduction in K concentration and stunted root and shoot growth
    • Knockout of OsHAK1 reduced the K absorption rate of unit root surface area by 50-55% and 30%, and total K uptake by 80% and 65% at 0
    • The root net high affinity K uptake of oshak1 mutants was sensitive to salt stress, but not to ammonium supply
    • Rice potassium transporter OsHAK1 is essential for maintaining potassium mediated growth and functions in salt tolerance over low and high potassium concentration ranges.
    • The positive relationship between K concentration and shoot biomass in the mutants suggests that OsHAK1 plays an essential role in K-mediated rice growth and salt tolerance over low and high K concentration ranges
    • Production of low-Cs(+) rice plants by inactivation of the K(+) transporter OsHAK1 with the CRISPR-Cas system.
    • Here, we show that inactivation of the Cs(+) -permeable K(+) transporter OsHAK1 with the CRISPR-Cas system dramatically reduced Cs(+) uptake by rice plants
    • Our results demonstrate that, in rice roots, potassium transport systems other than OsHAK1 make little or no contribution to cesium uptake
    • Phenotypic analysis of OsHAK1 overexpression seedlings (Ox) demonstrated that they present better tolerance to drought stress than wild-type (WT)
    • Under drought conditions, OsHAK1 knockout mutants (KO) presented lower tolerance to the stress and displayed stunted growth at both the vegetative and reproductive stages
    • Consequently, OsHAK1 can be considered to be used in molecular breeding for improvement of drought tolerance in rice
    • Recently, we reported that the high-affinity potassium transporter OsHAK1 plays important roles in K acquisition and translocation in rice over low and high K concentration ranges, however, knowledge on the regulatory roles of OsHAK1 in osmotic/drought stress is limited
    • Here, transcript levels of OsHAK1 were found transiently elevated by water deficit in roots and shoots, consistent with the enhanced GUS activity in transgenic plants under stress
    • Furthermore, qPCR analysis revealed that OsHAK1 act as a positive regulator of the expression of stress-responsive genes as well as of two well-known rice channel genes (OsTPKb and OsAKT1) involved in K homeostasis and stress responses in transgenic plants under dehydration
    • Seedlings over-expressing OsHAK1 were more tolerant than wild type, displaying a superior photosynthetic rate, a higher leaf chlorophyll content, an enhanced accumulation of proline and a reduced level of lipid peroxidation
    • Variation in the Abundance of OsHAK1 Transcript Underlies the Differential Salinity Tolerance of an indica and a japonica Rice Cultivar.
    • At the transcriptome level, the over-expression of OsHAK1 stimulated a number of stress-responsive genes as well as four genes known to be involved in Na+ homeostasis and the salinity response (OsHKT1;5, OsSOS1, OsLti6a and OsLti6b)
    • The level of expression of OsHAK1 was correlated with Na+/K+ homeostasis, which implies that the gene should be explored a target for molecular approaches to the improvement of salinity tolerance in rice
    • When the stress was applied at booting through to maturity, the OsHAK1 over-expressors out-yielded wild type by 25%, and no negative pleiotropic effects were expressed in plants gown under non-saline conditions
    • The impaired allocation of sugar to the roots and spikelets caused by the knocking out of OsHAK1 was accompanied by a down-regulation in the leaf sheaths and panicle axes of genes encoding sucrose transporters (SUT genes), which are active in the phloem, as well as in the roots and spikelets of those encoding monosaccharide transporters (MST genes), which transport hexose sugars across the plant plasma membrane
    • Here, a comparison between wild type rice and OsHAK1 knockout mutants not only confirmed the known detrimental effect of the absence of OsHAK1 on root growth, pollen viability and fertility, but also showed that sucrose phosphate synthase activity was lowered, and the sucrose content of the leaves was markedly increased, due to a partial block on the up-loading of sucrose into the phloem
    • OsHAK1 controls the vegetative growth and panicle fertility of rice by its effect on potassium-mediated sugar metabolism.
    • Both the vegetative growth and reproductive success of rice are compromised by the absence of a functional copy of the gene OsHAK1
    • The conclusion was that the failure to fully supply the demand of the mutant’s sink organs for assimilate was responsible for its compromised phenotype, and that the deficiency in K uptake induced by the loss of OsHAK1 functionality was responsible for the disruption of sugar metabolism
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