Functional Analysis Of Populus PagAFP2a In Response To Abiotic Stress

Abiotic stress is the most important factor affecting the growth and development of plants.Studies have shown that in arabidopsis thaliana AFP1 or AFP2 mutations can lead to increased sensitivity to ABA and enhanced resistance to salt stress.In rice,the Os AFP1 knockout mutant plants showed a significant increase in drought tolerance,salt stress tolerance and heat tolerance.These results indicate that AFPs is involved in a variety of stress responses in plants by negatively regulating ABA signaling.In this paper,the role of AFP genes in the resistance of poplar 84 K to abiotic stress was studied.Previous RNA-seq studies in the laboratory showed that under salt treatment conditions,the expression of AFPs in 84 K poplar showed a trend of first increasing and then decreasing with the extension of treatment time,indicating that its expression was induced by salt stress.Through conservative domain and evolutionary analysis,it was determined that 84 K poplar contains four At AFP homologous genes,named PagAFP2 a,PagAFP2 b,PagAFP3 a,and PagAFP3 b respectively.We chose the PagAFP2 a gene that reacted strongly and quickly during salt treatment to continue our research.Through RT-q PCR on 84 K poplar after stress treatment,it can be seen that with the extension of treatment time,the expression of PagAFP2 a first increased and then decreased.Suggesting that PagAFP2 a plays an important role in the process of poplar resistance to abiotic stress.To investigate whether the expression of PagAFP2 a gene is induced by ABA signals.We studied the expression pattern of PagAFP2 a gene after ABA treatment.The results showed that the expression of PagAFP2 a increased rapidly after ABA treatment.In addition,by analyzing the promoter of PagAFP2 a gene,it was found that its promoter region contains an ABRE domain,which is a binding site of the ABFs transcription factor family involved in the ABA signaling pathway.Yeast one hybrid has shown that the PagAREB1-3 can bind to the promoter fragment of the PagAFP2 a.This indicates that the expression of PagAFP2 a may be regulated by PagAREB1-3 and thus induced by ABA signals.To further explore the function of PagAFP2 a,we obtained PagAFP2 a overexpression transgenic plant and knockout transgenic plant through infection.Based on the analysis of the above transgenic plant,under normal growth conditions,there is no significant difference in the growth status between transgenic and wild plants.Under salt stress conditions,over-expressing PagAFP2 a plants showed earlier stress responses,more severe leaf damage,tip wilting,and overall plant damage compared to wild-type plants.The growth status of knockout plants is significantly better than that of wild-type plants,and the overall damage to the plants is relatively mild.Under drought stress,over-expressed plants exhibit earlier apical wilting and basal leaf drying due to dehydration.After rehydration,the leaves of wild-type plants unfold and wilting phenomenon weakens,which can restore normal growth.However,most of the old leaves in transgenic plants have withered and curled,and only the top leaves have recovered,resulting in severe drought stress damage.The results indicate that the PagAFP2 a plays a negative regulatory role in plant stress response.Overall,this study supplements the regulatory role of the PagAFP2 a in the growth stress process of poplar,providing important theoretical basis for the breeding of excellent poplar varieties.