为探究独脚金内酯抑制剂Tis108对天麻生长的影响,该研究采用10 μmol·L-1的Tis108溶液处理白麻块茎,对块茎的内源激素赤霉素(GA)含量进行测定,通过RT-PCR技术克隆GA失活关键酶GeCYP714A1基因,借助ExPASy、SWISS-MODEL、MEGA 等软件对该基因进行生物信息学分析,并测定其在天麻不同组织部位的表达水平.结果显示,Tis108处理后天麻块茎的GA含量显著升高,GA失活关键酶GeCYP714A1的转录水平显著降低.GeCYP714A 1基因的编码区全长1 173 bp,编码390个氨基酸,蛋白的相对分子质量为44.85 kDa,理论等电点为9.83,不稳定系数为49.20,脂肪系数为89.03,总平均亲水指数平均值为-0.235,属于碱性亲水性不稳定蛋白;且GeCYP714A1蛋白定位于线粒体,无信号肽,不具有跨膜结构.系统进化树分析显示,GeCYP714A1与铁皮石斛DcCYP714C2(PKU78454.1)蛋白亲缘关系最近,序列一致性达67.25％.利用qRT-PCR技术分析天麻GeCYP714A1基因的表达模式,结果显示在天麻块茎中GeCYP714A1转录水平最高,其次是茎和花序.该研究表明Tis108可抑制天麻块茎中GA失活酶GeCYP714A1的转录水平,提高GA的积累量,影响天麻块茎生长,为进一步揭示独脚金内酯调控天麻GA信号和块茎发育奠定基础.

Hormone-activated proteolysis is a recurring theme of plant hormone signaling mechanisms.In strigolac-tone signaling,the enzyme receptor DWARF14(D14)and an F-box protein,MORE AXILLARY GROWTH2(MAX2),mark SUPPRESSOR OF MAX21-LIKE(SMXL)family proteins SMXL6,SMXL7,and SMXL8 for rapid degradation.Removal of these transcriptional corepressors initiates downstream growth responses.The homologous proteins SMXL3,SMXL4,and SMXL5,however,are resistant to MAX2-mediated degradation.We discovered that the smxl4 smxl5 mutant has enhanced responses to strigolactone.SMXL5 attenuates strigolactone signaling by interfering with AtD14-SMXL7 interactions.SMXL5 interacts with AtD14 and SMXL7,providing two possible ways to inhibit SMXL7 degradation.SMXL5 function is partially dependent on an ethylene-responsive-element binding-factor-associated amphiphilic repression(EAR)motif,which typically mediates interactions with the TOPLESS family of transcriptional corepressors.However,we found that loss of the EAR motif reduces SMXL5-SMXL7 interactions and the attenuation of strigolactone signaling by SMXL5.We hypothesize that integration of SMXL5 into heteromeric SMXL complexes reduces the susceptibility of SMXL6/7/8 proteins to strigolactone-activated degradation and that the EAR motif pro-motes the formation or stability of these complexes.This mechanism may provide a way to spatially or temporally fine-tune strigolactone signaling through the regulation of SMXL5 expression or translation.

Modern semi-dwarf rice varieties of the"Green Revolution"require a high supply of nitrogen(N)fertilizer to produce high yields.A better understanding of the interplay between N metabolism and plant develop-mental processes is required for improved N-use efficiency and agricultural sustainability.Here,we show that strigolactones(SLs)modulate root metabolic and developmental adaptations to low N availabil-ity for ensuring efficient uptake and translocation of available N.The key repressor DWARF 53(D53)of the SL signaling pathway interacts with the transcription factor GROWTH-REGULATING FACTOR 4(GRF4)and prevents GRF4 from binding to its target gene promoters.N limitation induces the accumulation of SLs,which in turn promotes SL-mediated degradation of D53,leading to the release of GRF4 and thus promoting the expression of genes associated with N metabolism.N limitation also induces degradation of the DELLA protein SLENDER RICE 1(SLR1)in an D14-and D53-dependent manner,effectively releasing GRF4 from competitive inhibition caused by SLR1.Collectively,our findings reveal a previously unrecognized mecha-nism underlying SL and gibberellin crosstalk in response to N availability,advancing our understanding of plant growth-metabolic coordination and facilitating the design of the strategies for improving N-use effi-ciency in high-yield crops.

Phosphorus is an essential macronutrient for plant development and metabolism,and plants have evolved ingenious mechanisms to overcome phosphate(Pi)starvation.However,the molecular mechanisms underlying the regulation of shoot and root architecture by low phosphorus conditions and the coordinated utilization of Pi and nitrogen remain largely unclear.Here,we show that Nodulation Signaling Pathway 1(NSP1)and NSP2 regulate rice tiller number by promoting the biosynthesis of strigolactones(SLs),a class of phytohormones with fundamental effects on plant architecture and environmental responses.We found that NSP1 and NSP2 are induced by Oryza sativa PHOSPHATE STARVATION RESPONSE2(OsPHR2)in response to low-Pi stress and form a complex to directly bind the promoters of SL biosynthesis genes,thus markedly increasing SL biosynthesis in rice.Inter-estingly,the NSP1/2-SL signaling module represses the expression of CROWN ROOTLESS 1(CRL1),a newly identified early SL-responsive gene in roots,to restrain lateral root density under Pi deficiency.We also demonstrated that GR244DO treatment under normal conditions inhibits the expression of OsNRTs and OsAMTs to suppress nitrogen absorption but enhances the expression of OsPTs to promote Pi absorption,thus facilitating the balance between nitrogen and phosphorus uptake in rice.Importantly,we found that NSP1p:NSP1 and NSP2p:NSP2 transgenic plants show improved agronomic traits and grain yield under low-and medium-phosphorus conditions.Taken together,these results re-vealed a novel regulatory mechanism of SL biosynthesis and signaling in response to Pi starvation,providing genetic resources for improving plant architecture and nutrient-use efficiency in low-Pi environments.

Crop yield plays a critical role in global food security.For optimal plant growth and maximal crop yields,nutrients must be balanced.However,the potential significance of balanced nitrogen-iron(N-Fe)for improving crop yield and nitrogen use efficiency(NUE)has not previously been addressed.Here,we show that balanced N-Fe sufficiency significantly increases tiller number and boosts yield and NUE in rice and wheat.NIN-like protein 4(OsNLP4)plays a pivotal role in maintaining the N-Fe balance by coordi-nately regulating the expression of multiple genes involved in N and Fe metabolism and signaling.OsNLP4 also suppresses OsD3 expression and strigolactone(SL)signaling,thereby promoting tillering.Balanced N-Fe sufficiency promotes the nuclear localization of OsNLP4 by reducing H2O2 levels,reinforcing the func-tions of OsNLP4.Interestingly,we found that OsNLP4 upregulates the expression of a set of H2O2-scav-enging genes to promote its own accumulation in the nucleus.Furthermore,we demonstrated that foliar spraying of balanced N-Fe fertilizer at the tillering stage can effectively increase tiller number,yield,and NUE of both rice and wheat in the field.Collectively,these findings reveal the previously unrecognized ef-fects of N-Fe balance on grain yield and NUE as well as the molecular mechanism by which the OsNLP4-OsD3 module integrates N-Fe nutrient signals to downregulate SL signaling and thereby promote rice tillering.Our study sheds light on how N-Fe nutrient signals modulate rice tillering and provide potential innovative approaches that improve crop yield with reduced N fertilizer input for benefitting sustainable agriculture worldwide.

Arabidopsis MORE AXILLARY GROWTH2(MAX2)is a key component in the strigolactone(SL)and karrikin(KAR)signaling pathways and regulates the degradation of SUPPRESSOR OF MAX2 1/SMAX1-like(SMAX1/SMXL)proteins,which are transcriptional co-repressors that regulate plant architecture,as well as abiotic and biotic stress responses.The max2 mutation reduces resistance against Pseudomonas syringae pv.tomato(Pst).To uncover the mechanism of MAX2-mediated resistance,we evaluated the resistance of various SL and KAR signaling pathway mutants.The re-sistance of SL-deficient mutants and of dwarf 14(d14)was similar to that of the wild-type,whereas the resistance of the karrikin insensitive 2(kai2)mutant was compromised,demonstrating that the KAR signaling pathway,not the SL signaling pathway,positively regulates the immune re-sponse.We measured the resistance of smax1 and smxl mutants,as well as the double,triple,and quadruple mutants with max2,which revealed that both the smax1 mutant and smxl6/7/8 triple mutant rescue the low resistance phenotype of max2 and that SMAX1 accumulation diminishes resistance.The susceptibility of smax1D,con-taining a degradation-insensitive form of SMAX1,further confirmed the SMAX1 function in the re-sistance.The relationship between the accumu-lation of SMAX1/SMXLs and disease resistance suggested that the inhibitory activity of SMAX1 to resistance requires SMXL6/7/8.Moreover,the exogenous application of KAR2 enhanced resist-ance against Pst,but KAR-induced resistance de-pended on salicylic acid(SA)signaling.Inhibition of karrikin signaling delayed SA-mediated defense responses and inhibited pathogen-induced protein biosynthesis.Together,we propose that the MAX2-KAI2-SMAX1 complex regulates resistance with the assistance of SMXL6/7/8 and SA signaling and that SMAX1/SMXLs possibly form a multimeric complex with their target transcription factors to fine tune immune responses.

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目的:利用反向对接法探索独脚金内酯GR24在NF-κB信号通路抗炎作用的潜在药物作用靶点.方法:通过获取62个NF-κB信号通路的蛋白晶体学结构,构建NF-κB信号通路蛋白靶点结构数据库;使用分子对接软件AutoDock Vina,将GR24与结构数据库中的靶点进行反向分子对接模拟实验;根据对接分数和对接构象相互作用,筛选出潜在的药物靶点.结果:反向筛选得到3个与GR24具有高亲和性的靶蛋白PARP1、CK2和AKT;在对接构象的相互作用的比较中,PARP1优于CK2和AKT;与现有PARP1抑制剂相比,GR24有一定的相似性.结论:独脚金内酯GR24对PARP1、CK2和AKT靶蛋白具有竞争抑制的活性,该研究结果为独脚金内酯抗炎机制的研究提供重要的参考依据.

Tillering contributes to grain yield and plant architecture and therefore is an agronomically important trait in sorghum (Sorghum bicolor).Here,we identified and functionally characterized a mutant of the Nondormant Axillary Bud 1 (NAB1) gene from an ethyl methanesulfonate-mutagenized sorghum population.The nab1 mutants have increased tillering and reduced plant height.Map-based cloning revealed that NAB1 encodes a carotenoid-cleavage dioxygenase 7 (CCD7) orthologous to rice (Oryza sativa) HIGH-TILLERING DWARF1/DWARF17 and Arabidopsis thaliana MORE AXILLARY BRANCHING 3.NAB1 is primarily expressed in axillary nodes and tiller bases and NAB1 localizes to chloroplasts.The nab1 mutation causes outgrowth of basal axillary buds;removing these non-dormant basal axillary buds restored the wild-type phenotype.The tillering of nab1 plants was completely suppressed by exogenous application of the synthetic strigolactone analog GR24.Moreover,the nab1 plants had no detectable strigolactones and displayed stronger polar auxin transport than wild-type plants.Finally,RNA-seq showed that the expression of genes involved in multiple processes,including auxin-related genes,was significantly altered in nab1.These results suggest that NAB1 functions in strigolactone biosynthesis and the regulation of shoot branching via an interaction with auxin transport.

Dear Editor,Strigolactones (SLs) are a class of carotenoid-derived plant hormones that regulate shoot branching among other developmental processes (Gomez-Roldan et al.,2008;Umehara et al.,2008;Al-Babili and Bouwmeester,2015).In addition,SLs are released by roots as a chemical signal attracting symbiotic arbuscular mycorrhizal fungi.However,this signal is also perceived by seeds of root parasitic weeds,announcing the presence of a host and triggering germination (Al-Babili and Bouwmeester,2015).Natural SLs consist of a butenolide ring (D ring) connected by an enol ether bridge to a tricyclic lactone (ABC rings) in canonical SLs,such as strigol,and to a variable,second moiety in non-canonical SLs,such as methyl carlactonoate.There are around 25 known natural SLS (Xie,2016) that differ in the stereochemistry of the B/C junction and in modifications of the ABC-ring of canonical SLS,and in the structure of the second moiety of the non-canonical ones (Al-Babili and Bouwmeester,2015).Carlactone (CL),the central intermediate in SL biosynthesis,is a C19 molecule derived from all-trans-β-carotene by the sequential action of three enzymes through a stereospecific pathway.