Investigating the mechanisms of isochorismate synthase:An approach to improve salicylic acid synthesis and increase resistance to Fusarium head blight in wheat

Salicylic acid(SA),a vital endogenous hormone,plays a crucial role in plant growth and the response to abiotic and biotic stress.Isochorismate synthase(ICS)and phenylalanine ammonia lyase(PAL)are critical rate-limiting enzymes for SA synthesis.Fusarium head blight(FHB)seriously threatens the safety of wheat production,but increasing the content of SA can enhance FHB resistance.However,the pathway of SA synthesis and regulation in wheat remains unknown.In this study,three wheat ICS(TaICSA,TaICSB,and TaICSD)were identified,and their functions were validated in vitro for isomerizing chorismate to isochorismate.The mutation of one or two homoeoalleles of TaICSA,TaICSB,and TaICSD in the wheat variety‘Cadenza’reduced SA levels under ultraviolet treatment and Fusarium graminearum infection,further enhancing sensitivity to FHB.Overexpression of TaICSA can significantly enhance SA levels and resistance to FHB.To further study SA synthesis pathways in wheat and avoid interference with pathogenicity related genes,the leaves of wild-type Cadenza and different TaICS mutant lines were subjected to ultraviolet treatment for transcriptomic analysis.The results showed that 37 PALs might be involved in endogenous SA synthesis,and 82 WRKY and MYB family transcription factors may regulate the expression of ICS and PAL.These results were further confirmed by RT-PCR.In conclusion,this study expands our knowledge of SA biosynthesis and identifies TaICSA,as well as several additional candidate genes that encode transcription factors for regulating endogenous SA levels,as part of an efficient strategy for enhancing FHB resistance in wheat.

Bright single-photon sources in the telecom band by deterministically coupling single quantum dots to a hybrid circular Bragg resonator

High-performance solid-state quantum sources in the telecom band are of paramount importance for longdistance quantum communications and the quantum Internet by taking advantage of a low-loss optical fiber network.Here,we demonstrate bright telecom-wavelength single-photon sources based on In(Ga)As/Ga As quantum dots(QDs)deterministically coupled to hybrid circular Bragg resonators(h-CBRs)by using a wide-field fluorescence imaging technique.The QD emissions are redshifted toward the telecom O-band by using an ultra-low In As growth rate and an In Ga As strain reducing layer.Single-photon emissions under both continuous wave(CW)and pulsed operations are demonstrated,showing high brightness with count rates of 1.14 MHz and 0.34 MHz under saturation powers and single-photon purities of g^(2)(0)=0.11±0.02(CW)and g^(2)(0)=0.087±0.003(pulsed)at low excitation powers.A Purcell factor of 4.2 with a collection efficiency of 11.2%±1%at the first lens is extracted,suggesting efficient coupling between the QD and h-CBR.Our work contributes to the development of highly efficient single-photon sources in the telecom band for fiber-based quantum communication and future distributed quantum networks.