Physiological Response and Expression of Salt-tolerant Genes in Juglans cordiformis under NaCl Stress
[Objective]This study investigated the physiological characteristics and differential responses of ion transport and mitogen activated protein kinase(MAPK)cascade signaling genes in Juglans cordi-formes'Xinwen No.41'walnut seedlings under different NaCl stress conditions.[Methods]Pot planting was employed to explore the response of'Xinwen No.41'walnut seedlings with same growth to salt stress treatments with three salt concentrations-100,150,and 200 mmol·L-1 to.,and the water treatment was served as control group(CK).Following 20 days of treatment,the phenotypic and photosynthetic paramet-ers of the seedlings were measured.Non-invasive micro-test technology(NMT)was utilized to assess root Na+,K+,and H+fluxes.RNA was extracted from both leaves and roots for gene expression analysis re-lated to MAPK cascade signaling transduction and ion transport.Redundancy analysis(RDA)was em-ployed to explore the correlations between physiological indicators and gene expression,aiming to elucid-ate the salt stress response and regulatory mechanisms in walnut seedlings.[Results]Increasing salt con-centrations resulted in significant reductions in root volume and total biomass of the seedlings,accompan-ied by leaf withering and wilting.Photosynthetic parameters such as net photosynthetic rate,transpiration rate,and stomatal conductance exhibited declining trends,while the intercellular CO2 concentrations in-creased.Activities of superoxide dismutase(SOD),peroxidase(POD),ascorbate peroxidase(APX)activit-ies,Pro,MDA and H2O2 contents in leaves and roots increased significantly.Na+content in roots signific-antly accumulated and showed a clear trend of efflux with increasing salt concentration,while K+efflux and H+influx in leaves maintained intracellular osmotic potential homeostasis.Salt-tolerant-related genes,such as plasma membrane Na+/H+antiporter(SOS1)exhibited higher expression levels in leaves,while the So-dium/hydrogen antiporter 1(NHX1)was up-regulated and then down-regulated.Moreover,Vacuolar H+-ATPase subunit c(VHA-C1)was significantly up-regulated in roots.WRKY65(WRKY transcription factor 65),MKK9(Mitogen-activated protein kinase 9)and MPK3(Mitogen-activated protein kinase 3)gene in-creased at 100 mmol·L-1 stress,with higher expression levels observed in leaves compared to roots.[Con-clusion]Under NaCl stress,roots of Juglans cordiformis are more affected by stress than the leaves.Jr-SOS1,JrNHX1,and JrNHX2 are closely related to salt resistance and are key genes for resisting salt stress.
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