CRISPR/Cas9-mediated SNAC9 mutants reveal the positive regulation of tomato ripening by SNAC9 and the mechanism of carotenoid metabolism regulation

NAC transcriptional regulators are crucial for tomato ripening.Virus-induced gene silencing(VIGS)of SNAC9(SlNAC19,Gene ID:101248665)affects tomato ripening,and SNAC9 is involved in ethylene and abscisic acid(ABA)metabolic pathways.However,the function of SNAC9 in pigment metabolism in tomatoes remains unclear.This work seeks to discover the mechanism of SNAC9 involvement in pigment metabolism during tomato ripening by establishing a SNAC9 knockout model using CRISPR/Cas9 technology.The results indicated that fruit ripening was delayed in knockout(KO)mutants,and SNAC9 mutation significantly affected carotenoid metabolism.The chlorophyll(Chl)degradation rate,total carotenoid content,and lycopene content decreased significantly in the mutants.The transformation rate of chloroplasts to chromoplasts in mutants was slower,which was related to the carotenoid content.Furthermore,SNAC9 changed the expression of critical genes(PSY1,PDS,CRTISO,Z-ISO,SGR1,DXS2,LCYE,LCYB,and CrtR-b2)involved in pigment metabolism in tomato ripening.SNAC9 knockout also altered the expression levels of critical genes involved in the biosynthesis of ethylene and ABA.Accordingly,SNAC9 regulated carotenoid metabolism by directly regulating PSY1,DXS2,SGR1,and CrtR-b2.This research provides a foundation for developing the tomato ripening network and precise tomato ripening regulation.

Effects of dynamic deformation of pendant water drops on the electric field between hollow porcelain insulator sheds under extreme rainfall

Hollow porcelain insulators in substations are frequently confronted with rain flashovers under extreme rainfall.This study aims to investigate the spatial and temporal variation of electric fields between hollow porcelain insulator sheds affected by dynamic deformation of pendant water drops and effects of the dimensionless number of fluids,the Weber number(We)and the electric Bond number(BoE),on it for influencing factors'analysis.Flow‐electric field coupling simulations were carried out to compute the magnitude and the position of AC electric fields between the sheds.The results show that the maximum electric field at a point in time(Etmax)increases significantly after the breakup of the pendant water drop,and its position alters accordingly.For low We and BoE,the global maximum electric field(Egmax)increases with increasing We and BoE,respectively.It is much closer to the adjacent sheds and occurs later than Etmax at the breakup of the pendant water drop(Ebmax).By contrast,Egmax decreases in different degrees at high We and BoE,respectively.There is little difference between Egmax and Ebmax in the position and the occurring time.The influence mechanism on the maximum electric field and discharges and the relationship between discharges induced by the pendant water drop and rain flashover are discussed.