当植物遭受昆虫取食、极端天气及人为因素等导致的机械性损伤胁迫后,会迅速在转录及代谢水平上启动一系列的应答机制,引起植物内源激素及次生代谢物含量的变化.该研究以药用模式植物丹参为例,评估机械损伤对药用植物代谢的作用.运用qRT-PCR 及 LC-MS检测叶片损伤刺激下,胁迫响应的茉莉酸类物质(jasmonates,JAs)和丹参酮类成分生物合成基因以及含量的变化情况,得出处理后不同时序叶片与根部在转录和代谢水平上的相关规律,从而探讨丹参对机械损伤胁迫的响应机制.结果显示,机械损伤诱导能够瞬时提高JAs生物合成基因的表达,其中AOC与JAR在诱导后开始上升,在2 h达到最高,AOS与OPR3则在4 h达到最高,与之相应的OPDA、JA及JA-Ile的含量均在2 h达到最高.丹参酮生物合成中二萜合酶基因CPS1与KSL1均在2 h上升至最高,而后修饰CYP450s基因则均在4 h上升至最高,4种丹参酮的含量则均在8 h内呈现持续上升的趋势.该研究为揭示机械损伤对次生代谢积累的研究提供参考,为进一步了解机械损伤胁迫下JAs在增强植物抗性、促进活性成分积累和提高药材品质方面的作用奠定基础.

Jasmonates(JAs),a class of lipid-derived stress hormones,play a crucial role across an array of plant phys-iological processes and stress responses.Although JA signaling is thought to rely predominantly on the degradation of specific JAZ proteins by SCFCOI1,it remains unclear whether other pathways are involved in the regulation of JAZ protein stability.Here,we report that PUB22,a plant U-box type E3 ubiquitin ligase,plays a critical role in the regulation of plant resistance against Helicoverpa armigera and other JA re-sponses in tomato.Whereas COI1 physically interacts with JAZ1/2/5/7,PUB22 physically interacts with JAZ1/3/4/6.PUB22 ubiquitinates JAZ4 to promote its degradation via the 26S proteasome pathway.Impor-tantly,we observed that pub22 mutants showreduced resistance to H.armigera,whereasjaz4 single mu-tants and jaz1 jaz3 jaz4 jaz6 quadruple mutants have enhanced resistance.The hypersensitivity of pub22 mutants to herbivores could be partially rescued by JAZ4 mutation.Moreover,we found that expression of PUB22 can be transcriptionally activated by MYC2,thus forming a positive feedback circuit in JA signaling.We noticed that the PUB22-JAZ4 module also regulates other JA responses,including defense against B.cinerea,inhibition of root elongation,and anthocyanin accumulation.Taken together,these re-sults indicate that PUB22 plays a crucial role in plant growth and defense responses,together with COI1-regulated JA signaling,by targeting specific JAZs.

Salt stress is a major abiotic stress which severely hinders crop production.However,the regulatory network controlling tomato resistance to salt remains unclear.Here,we found that the tomato WRKY transcription factor WRKY57 acted as a negative regulator in salt stress response by directly attenuating the transcription of salt-responsive genes(SlRD29B and SlDREB2)and an ion homeo-stasis gene(SlSOS1).We further identified two VQ-motif containing proteins SlVQ16 and SlVQ21 as SlWRKY57-interacting proteins.SlVQ16 pos-itively,while SlVQ21 negatively modulated tomato resistance to salt stress.SlVQ16 and SlVQ21 com-petitively interacted with SlWRKY57 and antagonis-tically regulated the transcriptional repression activity of SlWRKY57.Additionally,the SlWRKY57-SlVQ21/SlVQ16 module was involved in the pathway of phytohormone jasmonates(JAs)by interacting with JA repressors JA-ZIM domain(JAZ)proteins.These results provide new insights into how the SlWRKY57-SlVQ21/SlVQ16 module finely tunes tomato salt tolerance.

Wheat(Triticum aestivum)is one of the most essential human energy and protein sources.However,wheat production is threatened by devastating fungal diseases such as stripe rust,caused by Puccinia striiformis Westend.f.sp.tritici(Pst).Here,we reveal that the alternations in chloroplast lipid profiles and the accu-mulation of jasmonate(JA)in the necrosis region activate JA signaling and trigger the host defense.The collapse of chloroplasts in the necrosis region results in accumulations of polyunsaturated membrane lipids and the lipid-derived phytohormone JA in transgenic lines of Yr36 that encodes Wheat Kinase START 1(WKS1),a high-temperature-dependent adult plant resistance protein.WKS1.1,a protein encoded by a full-length splicing variant of WKS1,phosphorylates and enhances the activity of keto-acyl thiolase(KAT-2B),a critical enzyme catalyzing the β-oxidation reaction in JA biosynthesis.The premature stop mutant,kat-2b,accumulates less JA and shows defects in the host defense against Pst.Conversely,overexpression ofKAT-2B results in a higher level of JA and limits the growth of Pst.Moreover,JA inhibits the growth and reduces pustule densities of Pst.This study illustrates the WKS1.1-KAT-2B-JA pathway for enhancing wheat defense against fungal pathogens to attenuate yield loss.

Jasmonates(JAs)are phytohormones that finely regulate critical biological processes,including plant development and defense.JASMONATE ZIM-DOMAIN(JAZ)proteins are crucial transcrip-tional regulators that keep JA-responsive genes in a repressed state.In the presence of JA-Ile,JAZ repressors are ubiquitinated and targeted for degradation by the ubiquitin/proteasome system,allowing the activation of downstream tran-scription factors and,consequently,the induction of JA-responsive genes.A growing body of evi-dence has shown that JA signaling is crucial in defending against plant viruses and their insect vectors.Here,we describe the interaction of C2 proteins from two tomato-infecting geminiviruses from the genus Begomovirus,tomato yellow leaf curl virus(TYLCV)and tomato yellow curl Sardinia virus(TYLCSaV),with the transcriptional repressor JAZ8 from Arabidopsis thaliana and its closest orthologue in tomato,SlJAZ9.Both JAZ and C2 proteins colocalize in the nucleus,forming dis-crete nuclear speckles.Overexpression of JAZ8 did not lead to altered responses to TYLCV in-fection in Arabidopsis;however,knock-down of JAZ8 favors geminiviral infection.Low levels of JAZ8 likely affect the viral infection specifically,since JAZ8-silenced plants neither display ob-vious developmental phenotypes nor present dif-ferences in their interaction with the viral insect vector.In summary,our results show that the geminivirus-encoded C2 interacts with JAZ8 in the nucleus,and suggest that this plant protein exerts an anti-geminiviral effect.

Jasmonates (JAs) orchestrate immune responses upon wound/herbivore injury or infection by necrotrophic pathogens.Elucidation of catabolic routes has revealed new complexity in jasmonate metabolism.Two integrated pathways attenuate signaling by turning over the active hormone jasmonoyl-isoleucine (JA-Ⅱe) through ω-oxidation or deconjugation,and define an indirect route forming the derivative 12OH-JA.Here,we provide evidence for a second 12OH-JA formation pathway by direct jasmonic acid (JA) oxidation.Three jasmonic acid oxidases (JAOs) of the 2-oxoglutarate dioxygenase family catalyze specific oxidation of JA to 12OH-JA,and their genes are induced by wounding or infection by the fungus Botrytis cinerea.JAO2 exhibits the highest basal expression,and its deficiency in jao2 mutants strongly enhanced antifungal resistance.The resistance phenotype resulted from constitutive expression of antimicrobial markers rather than from their higher induction in infected jao2 plants and could be reversed by ectopic expression of any of the three JAOs injao2.Elevated defense injao2 was dependent on the activity of JASMONATE RESPONSE 1 (JAR1) and CORONATINE-INSENSITIVE 1 (COI1) but was not correlated with enhanced JA-Ⅱe accumulation.Instead,jao2 mutant lines displayed altered accumulation of several JA species in healthy and challenged plants,suggesting elevated metabolic flux through JA-Ile.Collectively,these data identify the missing enzymes hydroxylating JA and uncover an important metabolic diversion mechanism for repressing basal JA defense responses.

萜类化合物是植物中的一类重要的次生代谢产物,在医药、工业和农业生产上扮演着重要的角色.由于一些重要的萜类具有复杂的化学结构以及在植物中的低含量,使其不能低成本地大量生产.因此,利用植物中普遍存在的茉莉素调控机制和外源介导相关转录因子,调控萜类生物合成途径关键酶基因表达,以达到提高目标萜类化合物含量,这已成为研究热点.本文综述了萜类化合物的生物合成途径、响应茉莉素信号且与次生代谢有关的转录因子以及应用茉莉素调控萜类化合物合成的研究进展,探讨了茉莉素调控萜类合成中所面临的问题,并对茉莉素调控萜类生物合成的潜在经济价值进行了展望.

水稻是我国最主要的粮食作物,在国民经济和生活中占据重要地位.在水稻的周年生产中,病虫害的控制最为关键.因此,了解水稻与病虫害的互作机理,对水稻的育种和生产具有重要指导意义.植物激素是在植物生命活动中必不可少,调控植物生长、发育、衰老等主要生理过程的一类有机分子.近年来,大量实验证据表明,在植物与病原物互作过程中,植物内源激素也发挥着重要作用.随着水稻抗病和感病的机理解析越来越多,有关植物激素所扮演的重要功能角色也愈发清晰.其中,水杨酸、茉莉酸和乙烯研究最为广泛,它们之间的相互拮抗或协同效应决定了植物对病原物的防御反应强度.其它激素如:油菜素内酯、赤霉素、生长素、细胞分裂素、脱落酸等,单独或者通过调控水杨酸、茉莉酸和乙烯信号分子转导网络也参与植物与病原物互作过程.本研究综述了各大植物激素在水稻抗病或感病中作用,并对其未来研究进行展望,以便为水稻病害的防治提供理论依据.

茉莉酸类物质作为植物体内源激素,能够诱导萜类、生物碱和黄酮类等多种药用活性成分在植物体内的生物合成,在植物次生代谢过程中发挥着非常重要作用.茉莉酸信号通路中的转录因子能通过与靶基因启动子中的顺式作用元件相互作用,激活或抑制植物次生代谢生物合成途径中多个关键酶基因的表达,有效地启动或关闭次生代谢生物合成途径,调控特定次生代谢产物的生物合成过程,从而影响次生代谢产物的积累.该文主要综述了茉莉酸信号通路中的转录因子(包括AP2/ERFs,bHLH,MYB,WRKY)在植物次生代谢中的调控作用等方面的研究进展,并探讨了转录因子在提高药用活性成分方面的潜在应用价值,为解析茉莉酸信号通路调控植物内的次生代谢过程提供参考和依据.

茉莉酸类化合物作为环境信号分子,不仅参与植物生长发育的调控,同时受到环境胁迫的诱导,参与植物对逆境胁迫的响应和防御.本研究以北方广泛种植的玉米品种'郑单958'为材料,通过对根系外源施加茉莉酸甲酯的方式,探究干旱胁迫下茉莉酸甲酯对玉米幼苗抗旱性以及根系吸水的影响.结果表明,外源茉莉酸甲酯可提高玉米幼苗光合速率、蒸腾作用和气孔导度,增强抗氧化酶活性,降低H2O2和丙二醛的含量,从而缓解干旱胁迫对植株造成的损伤.通过测定根系水导、氯化汞处理的蒸腾速率的变化以及水通道蛋白的表达量,发现干旱胁迫下外源茉莉酸甲酯可增强根系水通道蛋白的表达,进而增强玉米幼苗的根系吸水能力,从而缓解干旱胁迫造成的叶片水分含量的下降和水势的降低,提高了玉米幼苗的抗旱性.