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    Home > Biochemistry News > Biotechnology News > Lin Hongxuan's research group reveals a new mechanism by which G protein regulates wax synthesis through calcium signaling and thus regulates heat tolerance in rice

    Lin Hongxuan's research group reveals a new mechanism by which G protein regulates wax synthesis through calcium signaling and thus regulates heat tolerance in rice

    • Last Update: 2022-03-08
    • Source: Internet
    • Author: User
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      Global warming has become a major issue threatening the world's food security.
    It is reported that every 1°C increase in the annual average temperature will reduce the yield of rice, wheat, corn and other food crops by about 3% to 8%
    .
    In the long-term confrontation with high temperature, plants have evolved different coping mechanisms: on the one hand, plants can improve their ability to scavenge unfolded proteins by "actively responding", thereby maintaining protein homeostasis and obtaining high temperature resistance.
    (such as TT1 ) (Li et al.
    , 2015); on the other hand, plants can also inactivate themselves by "static braking", reduce thermal response consumption, maintain normal physiological activities, and reduce heat stress.
    Rebuilds quickly after the end to improve survivability under heat stress
    .
    It is of great significance for the genetic improvement of high temperature resistance of crops to mine the natural loci of high temperature resistance and conduct in-depth research on its regulatory mechanism by genetic means
    .

      G protein has always been a research hotspot in plant growth, development and stress response, but its molecular mechanism of heat stress tolerance has not been deeply studied; calcium signal, as a second messenger, plays an important role in the process of stress signal transduction However, there is still no plausible explanation for how calcium signals are decoded downstream of the thermal signaling pathway and transduced into physiological and biochemical responses
    .
    Natural loci have received extensive attention due to their importance in production applications, but their localization is difficult, especially for loci related to complex traits such as heat tolerance
    .
    Following the successful positioning and cloning of the first heat-resistant QTL locus TT1 in rice in 2015 , Lin Hongxuan's research group recently successfully isolated and cloned the heat-resistant QTL TT2 in rice .
    The related research paper was published on December 31, 2021, with the title " TT2 controls rice thermotolerance through SCT1-dependent alteration of wax biosynthesis" was published in the journal Nature Plants
    .
    This result revealed a new pathway for the regulation of heat resistance in rice that combines G protein, calcium signaling, and wax metabolism at the molecular level
    .

    The research group positioned and cloned TT2  from the heat-tolerant genetic resources of rice by forward genetics , which encodes a G protein γ subunit and negatively regulates the heat resistance of rice; there is a SNP in TT2 derived from tropical japonica, which makes It encodes a prematurely terminated form of the protein and acquires strong heat tolerance, while the proportion of this SNP is low in high temperature-sensitive temperate japonica rice
    .
    Under heat stress, compared with the control, the near-isogenic line NIL- TT2 HPS32 carrying the heat tolerance locus significantly improved the seedling survival rate, and the yield per plant at the mature stage also increased significantly, with an increase of 54.
    7%, indicating that the Genetic loci have important application value in agricultural production
    .
    Further research found that the function of TT2 affects the wax metabolism pathway after heat stress.
    In the heat-sensitive control lines, the wax-related regulatory genes showed an obvious trend of being down-regulated by heat induction, while in heat-resistant In the NIL- TT2 HPS32 line, some wax genes showed a trend of stable expression that did not respond to heat, including an important transcription factor OsWR2 that positively regulates wax synthesis
    .
    Knockout of OsWR2 in the heat-resistant NIL- TT2 HPS32 line found that its heat-tolerant phenotype disappeared, proving that maintaining normal wax content under heat stress is critical for heat tolerance in rice
    .
    In order to further establish the regulatory relationship between the expression levels of TT2 and OsWR2, the researchers discovered the CG1-like motif of the binding element of a class of calmodulin-binding transcription factors (CAMTA) by analyzing the upstream promoter of OsWR2, and aligned them by homology.
    , found two members of the CAMTA family in rice and named them SCT1 and SCT2; further experiments proved that SCT1 can directly bind to the promoter of OsWR2, affect the expression of OsWR2, and negatively regulate the heat tolerance of rice
    .
    SCT1 has a calcium-dependent calmodulin (CaM) binding site, which can decode intracellular calcium signals by interacting with CaM
    .
    G proteins have been previously reported to be involved in the regulation of calcium signaling in animals and plants (such as RGA1) (Ma et al.
    , 2015), and this study also confirmed that the loss of function of TT2 leads to the attenuation of heat-induced calcium signaling
    .
    In the presence of normal functioning TT2, high temperature induces the generation of calcium signals and increases the intracellular calcium concentration.
    The high concentration of calcium ions is sensed by CaM and promotes the interaction between CaM and SCT1, thereby enhancing the effect of CaM on SCT1 transcriptional activity.
    Inhibition eventually led to the rapid down-regulation of OsWR2 expression under high temperature conditions, the reduction of wax content and the final inability to resist high temperature, showing a heat-sensitive phenotype
    .
    When the function of TT2 is lost, the heat-induced calcium signal is weakened, which in turn weakens the interaction between SCT1 and CaM, reduces the inhibition of SCT1 transcriptional activity by CaM, and finally maintains the normal expression and stable wax content of OsWR2 under high temperature stress.
    , showing a heat resistant phenotype
    .

      In summary, this study is the first to systematically link G protein regulation, calcium signal transduction and decoding, and wax metabolism pathways, and elucidate a regulatory pathway from upstream signal generation to downstream physiological and biochemical responses, which is independent of previous studies.
    The known regulation of plant heat resistance through heat shock protein, reactive oxygen species scavenging and unfolded protein scavenging is an important progress in the field of plant heat resistance
    .
    TT2 is a precious genetic resource for heat-resistant breeding of crops, and it is of great significance for future crops to achieve targeted heat-resistant genetic improvement by means of molecular design
    .

      It is worth mentioning that during the review process of the paper, all three reviewers spoke highly of the work; in view of the importance of this work, Nature Plants published a paper written by Dr.
    Scott Hayes of Wageningen University in the Netherlands online at the same time.
    A review article entitled "Wrapped up against the heat" commented and looked forward to the results
    .
    Dr.
    Scott Hayes commented on the above research results and pointed out that the paper is an important progress in the field of heat resistance research; and pointed out that the discovered genes provide exciting potential targets for plant breeding and gene editing, which can help We address food security concerns on a rapidly warming planet
    .

      Kan Yi, a postdoctoral fellow at the Center for Excellence in Molecular Plant Science, Chinese Academy of Sciences, is the first author, and researcher Lin Hongxuan is the corresponding author
    .
    The center Mu Xiaorui, Zhang Hai, Gao Jin, Shan Junxiang and Ye Wangwei participated in the research work
    .
    This work was funded by the National Foundation of China, the Chinese Academy of Sciences, and the Guangdong Provincial Laboratory of Lingnan Modern Agriculture
    .

      Paper link: https:// align="center">  

    The TT2 HPS32 locus   from tropical japonica makes rice exhibit an obvious high temperature resistant phenotype at seedling and mature stages

      

      A schematic model of the regulation of heat tolerance in rice by the TT2-SCT1/SCT2-WR2 pathway under high temperature stress

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