ScCBF1 And StCBF1 Have Different Function In Response To Freezing,Drought And Salt Stresses In Potato

Solanum tuberosum（short for St）is a common cultivated potato,however,St-type potato is a freezing-sensitive variety and can not be cold-acclimated.In the cultivation process,it often suffers various abiotic stresses such as low temperature and drought.Solanum commersonii（short for Sc）is a wild-type potato with strong antifreeze and cold acclimation ability.CBF/DREB transcription factors play a key role in response to various abiotic stresses such as freezing and drought.In order to study whether the difference in frost resistance of St-and Sc-type potato is related to CBF1 transcription factor,we transferred StCBF1 and ScCBF1 genes to wild-type potato to obtain plants that overexpressing CBF1 gene.In this study,wild type and transgenic lines which have similar gene expression levels were used for subsequent experiments.By observing the growth phenotype of the plants under normal or stress conditions and measuring the relevant physiological and biochemical indicators,the differences in stress resistance between wild-type and transgenic plants were analyzed.The main results are as follows:（1）Overexpression of CBF1 gene in potato affected plant growth and development.The overexpression of ScCBF1 gene only had a little adverse effect on the early stage of plant growth,and the yield of tubers decreased slightly.However,overexpression of StCBF1 gene resulted in severe growth retardation and significantly decreased tuber yield.（2）Overexpression of ScCBF1/StCBF1 genes could enhance the freezing resistance of potato,but the freezing resistance of ScCBF1 plants was stronger than that of StCBF1 plants.Transgenic plants,especially ScCBF1 plants,can maintain higher membrane lipid unsaturation,lower electrolyte leakage,and lower cell membrane oxidation under cold stress.LT₅₀ experiments showed that the ScCBF1 plants had the strongest antifreeze ability,their LT₅₀0 was-4.5°C;the frost resistance of StCBF1 plants was slightly enhanced,their LT₅₀ was-3.2°C;the LT₅₀ of WT plants was-2.5°C.（3）Compared with the wild type,the drought resistance of the transgenic plants were significantly enhanced.In addition,the ScCBF1 plants also showed strong salt resistance.After drought stress,the water loss rate and MDA content of transgenic plants,especially ScCBF1 plants,were significantly lower than those of wild-type plants.Phenotypic analysis revealed that the leaves of wild-type plants first appeared a wilting phenotype,followed by StCBF1 plants,and the ScCBF1 plants showed a wilting phenotype at the latest.Under 200mM·L^-1salt stress,only ScCBF1 plants could root and grow.The results of NMT test showed that the dynamic balance of Na⁺and K⁺transportation in root tip of WT and StCBF1 plants was disrupted and K⁺/Na⁺decreased under salt stress,K⁺/Na⁺ratio decreased.After stress treatment,the Na⁺efflux of ScCBF1 plants increased and the K⁺uptake increased,which could maintain the higher K⁺/Na⁺ratio in the cells and reduce the toxicity of Na⁺to cells.（4）Under low temperature or drought stress conditions,the transgenic plants,especially ScCBF1 plants,had higher chlorophyll content and Gs compared to the wild type plants,and therefore could maintain a higher Pn.The PSII chlorophyll fluorescence of all lines were changed after stress treatment.The chlorophyll fluorescence parameters of transgenic plants,such as V_I,V_J,ABS/RC,TR_O/RC and DI_O/RC were significantly lower than that of wild type,however,Fv/Fm and ET_O/RC were significantly higher than WT plants.This indicates that under stress conditions,transgenic plants can maintain higher energy efficiency,reduce energy dissipation and maintain higher PSII activity.（5）Under normal or stress conditions,transgenic plants,especially ScCBF1 plants,can maintain higher APX,POD,CAT and SOD activity;reduce superoxide anion and hydrogen peroxide accumulation in plants,thereby reducing the damage of active oxygen on the membrane and photosynthetic system.（6）ScCBF1 and StCBF1 transcription factors can affect the expression of many stress and metabolism-related genes.They can not only directly regulate the expression of COR gene,but also can affect the expression of other metabolic processes related genes,such as fatty acid metabolism-related genes,antioxidant enzyme-related genes,photosynthesis key enzyme-related genes.