A novel ABA structural analogues enhanced plant resistance by inducing the plant immunity and inactivating ABA signaling pathway

Abscisic acid(ABA)is a phytohormone that not only important for plant growth,but also mediating the stress response.The roles of ABA in plant immunity are especially multifaceted.Recently,the ABA functional analogues are of great significance to promote its application.Here,we reported an ABA functional analogue named 167A.167A inhibits plant growth and seeds germinating of Arabidopsis.Meanwhile,the 167A enhanced the plant immunity,which is opposite of ABA.We further investigated the PTI-response after 167A treatment,and the results show that the ROS burst,callose deposition accumulate with 167A treatment.Moreover,167A also influence the degree of stomal closed.RNA-seq assays show that the 167A down-regulated the ABA associated genes and upregulated the JA/SA/ET associated genes.Through genetic analysis,the 167A modulating the plant resistance through the PYR/PYL Receptors.Together,these results demonstrate that a novel ABA analogue 167A positive regulated plant immunity and has great potential for agricultural applications.

Photoreduction of CO_(2) in the presence of CH_(4) over g-C_(3)N_(4) modified with TiO_(2) nanoparticles at room temperature

CO_(2)reduction under simulated sunlight over photocatalysts has become an attractive researcher area recently.In this work,carbon nitride compounds modified by TiO_(2)nanoparticles(TNPs)have been used for the photoreduction of CO_(2)in the presence of CH_(4)at room temperature.Briefly,a series of noble-metal-free TNP-graphitic-carbon nitride(g-C_(3)N_(4),also abbreviated CN)photocatalysts with different TNPs loadings and calcination temperatures have been synthesized by a wet-chemical method.The characterization results of XRD,FTIR,SEM,TEM,BET,XPS,CO_(2)Adsorption,UV-vis,and PL demonstrate that the BET surface area and CO_(2)adsorption capacity have been improved after the calcination.Besides,the g-C_(3)N_(4)has been successfully coupled with the TNPs and a heterojunction has formed at their interface.These characters contribute to increase the photocatalytic activity of TNPs-CN toward reducing CO_(2)in the presence of CH_(4),and its'performance is better than bare g-C_(3)N_(4),Titania(P_(25))-CN,MgO-CN,or Cu_(2)O-CN.Orthogonal experiments are then carried out to investigate the sensitivity factors and optimum conditions.The sensitivity results show that the reaction pressure makes little difference on the photocatalysis results,which verifies the photoinduced CO_(2)-CH_(4)reaction has a tiny change in gas volume.In addition,under the optimum conditions,the turnover frequency(TOF)of CO after 4 h reaction can reach 9.98μmol g-cat.^(-1)h^(-1),and traces of ethane and ethylene have been detected during the reactions.In addition,surface acetate and carbonaceous deposit are found on the(20)TNPs-CN/450 surface after continuous 24 h irradiation under the optimum conditions,which resulting in the inactivation of the catalyst.Finally,possible reaction mechanisms have been proposed based on the results.

SlMYB1 regulates the accumulation of lycopene, fruit shape, and resistance to Botrytis cinerea in tomato

Fruit lycopene,shape,and resistance are essential traits in vegetables whose final product is fruit,and they are also closely related to and strictly regulated by multiple transcription factors.Lycopene,which cannot be synthesized by the human body and can only be ingested from the outside,was important in maintaining human health.During fruit ripening and post-harvest,tomato plants face a variety of biotic or abiotic stresses,which might inf lict great damage to fruit quality due to its f lat shape and pointed tip during storage and transportation.Therefore,there is an urgent need for key molecular switches to simultaneously improve fruit lycopene and resistance to biotic stress during ripening.Here,we identified the MYB transcription factor SlMYB1 in tomato plants which could bind to the promoters of lycopene synthesis-related genes,SlLCY1,SlPSY2,and the pathogen-related gene SlPR5 directly,to regulate the fruit lycopene and resistance to Botrytis cinerea in tomato.In addition to regulating lycopene synthesis,SlMYB1 also regulates the content of soluble sugar,soluble protein and f lavonoid in tomato.What’s more,SlMYB1 could regulate the tomato fruit shape,making it smoother or f latter to prevent skin damage caused by vibration on fruits.RNA sequencing(RNA-seq)further showed that SlMYB1 fruit-specific expression lines had multiple differentially expressed genes compared with those from wild-type plants,suggesting that SlMYB1 might have multiple roles in fruit nutritional quality control and resistance to stresses,which is a rare occurrence in previous studies.In summary,our results revealed that SlMYB1 was an essential multi-functional transcription factor that could regulate the lycopene and resistance to Botrytis cinerea,and change the shape of fruit in tomato plants.

Recognition of the inducible,secretory small protein OsSSP1 by the membrane receptor OsSSR1 and the co-receptor OsBAK1 confers rice resistance to the blast fungus

The plant apoplast,which serves as the frontline battleground for long-term host–pathogen interactions,harbors a wealth of disease resistance resources.However,the identification of the disease resistance proteins in the apoplast is relatively lacking.In this study,we identified and characterized the rice secretory protein OsSSP1(Oryza sativa secretory small protein 1).OsSSP1 can be secreted into the plant apoplast,and either in vitro treatment of recombinant OsSSP1 or overexpression of OsSSP1 in rice could trigger plant immune response.The expression of OsSSP1 is suppressed significantly during Magnaporthe oryzae infection in the susceptible rice variety Taibei 309,and OsSSP1-overexpressing lines all show strong resistance to M.oryzae.Combining the knockout and overexpression results,we found that OsSSP1 positively regulates plant immunity in response to fungal infection.Moreover,the recognition and immune response triggered by OsSSP1 depend on an uncharacterized transmembrane OsSSR1(secretory small protein receptor 1)and the key co-receptor OsBAK1,since most of the induced immune response and resistance are lost in the absence of OsSSR1 or OsBAK1.Intriguingly,the OsSSP1 protein is relatively stable and can still induce plant resistance after 1 week of storage in the open environment,and exogenous OsSSP1 treatment for a 2-week period did not affect rice yield.Collectively,our study reveals that OsSSP1 can be secreted into the apoplast and percepted by OsSSR1 and OsBAK1 during fungal infection,thereby triggering the immune response to enhance plant resistance to M.oryzae.These findings provide novel resources and potential strategies for crop breeding and disease control.

The MYB transcription factor OsMYBxoc1 regulates resistance to Xoc by directly repressing transcription of the iron transport gene OsNRAMP5 in rice

Bacterial leaf streak caused by Xanthomonas oryzae pv.oryzicola(Xoc)is a continuous threat to rice cultivation,leading to substantial yield losses with socioeconomic implications.Iron ions are essential mineral nutrients for plant growth,but little information is available on how they influence mechanisms of rice immunity against Xoc.Here,we investigated the role of the myeloblastosis-related(MYB)transcriptional repressor OsMYBxoc1 in modulation of rice resistance through control of iron ion transport.Overexpression of OsMYBxoc1 significantly increased rice resistance,whereas OsMYBxoc1 RNA-interference lines and knockout mutants showed the opposite result.Suppression of OsMYBxoc1 expression dampened the immune response induced by pathogen-associated molecular patterns.We demonstrated that OsMYBxoc1 binds specifically to the OsNRAMP5 promoter and represses transcription of OsNRAMP5.OsNRAMP5,a negative regulator of rice resistance to bacterial leaf streak,possesses metal ion transport activity,and inhibition of OsMYBxoc1 expression increased the iron ion content in rice.Activity of the iondependent H2O2 scavenging enzyme catalase was increased in plants with suppressed expression of OsMYBxoc1 or overexpression of OsNRAMP5.We found that iron ions promoted Xoc infection and interfered with the production of reactive oxygen species induced by Xoc.The type Ⅲ effector XopAK directly inhibited OsMYBxoc1 transcription,indicating that the pathogen may promote its own proliferation by relieving restriction of iron ion transport in plants.In addition,iron complemented the pathogenicity defects of the RS105_DXopAK mutant strain,further confirming that iron utilization by Xoc may be dependent upon XopAK.In conclusion,our study reveals a novel mechanism by which OsMYBxoc1 modulates rice resistance by regulating iron accumulation and demonstrates that Xoc can accumulate iron ions by secreting the effector XopAK to promote its own infection.

The bacterial effector AvrRxo1 inhibits vitamin B6 biosynthesis to promote infection in rice

Xanthomonas oryzae pv.oryzicola(Xoc),which causes rice bacterial leaf streak,invades leaves mainly through stomata,which are often closed as a plant immune response against pathogen invasion.How Xoc overcomes stomatal immunity is unclear.Here,we show that the effector protein AvrRxo1,an ATPdependent protease,enhances Xoc virulence and inhibits stomatal immunity by targeting and degrading rice OsPDX1(pyridoxal phosphate synthase),thereby reducing vitamin B6(VB6)levels in rice.VB6 is required for the activity of aldehyde oxidase,which catalyzes the last step of abscisic acid(ABA)biosynthesis,and ABA positively regulates rice stomatal immunity against Xoc.Thus,we provide evidence supporting a model in which a major bacterial pathogen inhibits plant stomatal immunity by directly targeting VB6 biosynthesis and consequently inhibiting the biosynthesis of ABA in guard cells to open stomata.Moreover,AvrRxo1-mediated VB6 targeting also explains the poor nutritional quality,including low VB6 levels,of Xoc-infected rice grains.

Multiple forms of vitamin B_(6) regulate salt tolerance by balancing ROS and abscisic acid levels in maize root

Salt stress causes osmotic stress,ion toxicity and oxidative stress,inducing the accumulation of abscisic acid(ABA)and excessive reactive oxygen species(ROS)production,which further damage cell structure and inhibit the development of roots in plants.Previous study showed that vitamin B_(6)(VB_(6))plays a role in plant responses to salt stress,however,the regulatory relationship between ROS,VB_(6) and ABA under salt stress remains unclear yet in plants.In our study,we found that salt stress-induced ABA accumulation requires ROS production,in addition,salt stress also promoted VB_(6)(including pyridoxamine(PM),pyridoxal(PL),pyridoxine(PN),and pyridoxal 5′-phosphate(PLP))accumulation,which involved in ROS scavenging and ABA biosynthesis.Furthermore,VB_(6)-deficient maize mutant small kernel2(smk2)heterozygous is more susceptible to salt stress,and which failed to scavenge excessive ROS effectively or induce ABA accumulation in maize root under salt stress,interestingly,which can be restored by exogenous PN and PLP,respec-tively.According to these results,we proposed that PN and PLP play an essential role in balancing ROS and ABA levels under salt stress,respectively,it laid a foundation for VB_(6) to be better applied in crop salt resistance than ABA.