Physiological And Molecular Responses To Ca-K Mediated Cd/Zn Interactions In Polish Wheat Seedlings(Triticum Polonicum L.)

Cadmium(Cd),a non-essential element,is one of the most toxic heavy metals for living organisms,and is easily transported from soil to plant.Cd is potentially harmful in human health through the food chain.Zn is the same ethnic element as Cd.Moreover,Zn and Cd naturally coexist in soil.Zn can affect the absorption or the accumulation of Cd in plants.Ca and K could regulate Cd and(or)Zn uptake and transport in plants.Ca and K alleviate Cd toxicity,and improve the tolerance to Cd and Zn.Combining application of Ca and K(hereafter Ca-K)is more effective in reducing Cd uptake and alleviating Cd toxicity.Dwarf Polish wheat(DPW,Triticum polonicum L.),shows high tolerance to Cd and Zn,and inhibits of Cd and Zn uptake by each other.However,it is unknown that Ca-K mediates Cd/Zn interactions in physiological and molecular responses.Therefore,the aims of this study were to understand physiological and molecular responses to Ca-K mediate Cd/Zn interactions in Polish wheat seedlings by using determination of metal content,translocation of metals,subcellular distribution of metals,Cd chemical forms and RNA-sequencing(RNA-Seq).The main results are summarized as below:(1)The high concentration of Ca-K reduced the concentration of Cd and Zn in roots.The high concentration of Ca-K increased the Cd concentration,and reduced the Zn concentration in shoots,and the TFs of Cd and Zn were both increased.The high concentration of Ca-K significantly reduced the uptake of Cd and Zn by roots,it also notably reduced the root length under Cd and Zn stresses.Thus,the reduced uptake of Cd and Zn in response to Ca-K was mediated through reduction in the capacity of the roots to acquire Cd and Zn.These results indicated that high concentration of Ca-K decreased Cd and Zn uptake but promoted their translocation.A low or high concentration of Ca-K,Zn inhibited Cd uptake,promoted Cd translocation.The high concentration of Ca-K alleviated the reduction in Cd uptake and the promotion of Cd translocation caused by Zn.Cd decreased Zn uptake,inhibited Zn translocation,and the high concentration of Ca-K increased the promotion of Zn uptake and the reduction in Zn translocation.(2)Ca-K mediated Cd/Zn interactions by regulating gene expression and changing Cd/Zn subcellular distribution and Cd chemical forms.Treatment with Ca-K or Zn affected expression of several metal transporters such as ABC transporters,HMA2,HMA5,and influenced cell wall metabolism,the acquisition capacity and subcellular distribution of Cd,and the Cd chemical forms.Treatment with Ca-K or Cd affected expression of several metal transporters such as VIT,ABC transporters,HMA5,and influenced cell wall metabolism,and changed the subcellular distribution of Zn.