4种无患子科植物的SMXL家族全基因组鉴定、进化及DlSMXLs在龙眼体胚发生过程中的表达分析

【目的】为研究无患子科SMXL家族的生物学特性提供理论参考,深入探究该基因家族在无患子科植物非生物胁迫响应中的调控机制。【方法】基于模式植物拟南芥SMXL家族的氨基酸序列,利用TBtools对龙眼、红毛丹、无患子和荔枝的SMXL家族成员进行全基因组鉴定,Expasy、MEGA11等软件用于4种无患子科植物的进化和功能分析,同时利用龙眼转录组数据进行体胚发生早期阶段的表达分析。【结果】4种无患子科植物共鉴定出48个SMXL家族成员,其中龙眼11个、红毛丹11个、无患子9个以及荔枝17个。依据拟南芥SMXL家族成员的分类,将4种无患子科SMXL家族成员分为5个亚族且亚细胞定位于叶绿体、细胞核、细胞质或线粒体。蛋白互作分析表明,无患子科SMXL家族成员可能与多种蛋白存在互作关系,主要分为两类:一种是与受到非生物胁迫时大量表达的热休克蛋白(HSPs)或CLPs互作;另一种是与独角金内酯受体蛋白D14、karrikins受体蛋白KAI2和调控SL信号传导途径的蛋白MAX2进行互作。启动子顺式作用元件分析表明,4种无患子科植物SMXL家族成员存在较多的光响应元件、抗氧化反应元件(ARE)和脱落酸响应元件(ABRE)等,推测该基因家族广泛参与非生物胁迫响应。此外,DlSMXL家族成员在龙眼体胚发生早期存在5种不同的表达模式,其中DlSMXL4基因家族成员在胚性愈伤组织(EC)、不完全胚性紧实结构(ICpEC)和球形胚(GE)阶段相较其他成员呈现较高表达。基于5-氮胞苷、PEG、SL、光、温度和各种激素处理龙眼EC时期转录组数据分析可知,龙眼DlSMXL5在干旱、GR24、黑暗和高温处理下表达量均明显增加,推测该成员能够通过响应植物激素和应激胁迫维持胚性愈伤组织形态。其次DlSMXL8在5-氮胞苷处理时表达上调,推测其可能参与DNA甲基化在龙眼体胚发生过程中发挥作用。【结论】4种无患子科植物SUPPRESSOR OF MAX2-LIKE(SMXL)家族除了在植物生长发育过程种发挥重要的作用,同时还广泛参与植物非生物胁迫调控过程。本研究结果为无患子科植物中SMXL的分类和生物学功能提供了理论依据,并为SMXL在龙眼早期体细胞胚胎发生中的功能验证提供了更好的认识。

独脚金内酯抑制因子D53/SMXLs基因的研究进展

独脚金内酯(strigolactones,SLs)是一种新型的植物激素,参与调节植物分枝、生殖发育及叶片衰老等多种生物学过程。D53/SMXLs是独角金内酯信号转导通路中的抑制因子,在独脚金内酯信号转导中起重要作用。介绍了国内外最新关于独脚金内酯信号抑制因子D53/SMXLs的进展,综述了D53/SMXLs的发现、结构、信号转导机制、分子生物学功能及其他功能的研究成果。最后从三方面指出独脚金内酯信号途径有待完善与研究的内容。

BES1 Functions as the Co-regulator of D53-like SMXLs to Inhibit BRC1 Expression in Strigolactone-Regulated Shoot Branching in Arabidopsis

Shoot branching,determining plant architecture and crop yield,is critically controlled by strigolactones(SLs).However,how SLs inhibit shoot branching after its perception by the receptor complex remains largely obscure.In this study,using the transcriptomic and genetic analyss as well as biochemical studies,we reveal the key role of BES1 in the SL-regulated shoot branching.Wedemonstrate that BES1 and D53-like SMXLs,the substrates of SL receptor complex D14–MAX2,interact with each other to inhibit BRC1 expression,which specifically triggers the SL-regulated transcriptional network in shoot branching.BES1 directly binds the BRC1 promoter and recruits SMXLs to inhibit BRC1 expression.Interestingly,despite being the shared component by SL and brassinosteroid(BR)signaling,BES1 gains signal specificity through different mechanisms in response to BR and SL signals.

东利Hi型和苏尔士SMX、SMXL型静态混合器

一、概述静态混合的概念,对于许多工程技术人员来说还比较陌生,它是相对于动态混合(搅拌而提出来的。在一些化工过程中,例如混合、乳化、液～液苹取和液～液反应中,为了达到使互不相容的液体分散成液滴的目的,使用了搅拌器。搅拌器由电动机带动在搅拌槽内不断地运动,这种混合方式称之为动态混合。所谓静态混合,

Genome-wide identification, phylogenetic and expression analysis of SMAX1-Like genes in rapeseed(Brassica napus L.)

SMAX1-LIKE(SMXL) family members have played important roles in regulating plant growth and development in Arabidopsis and rice, but few have been studied in Brassica napus(rapeseed). In this study, 31 SMXL genes(BnaSMXL) were identified in rapeseed by whole genome bioinformatics. Detailed information were characterized, including genomic distribution, phylogenetic relationship, evolutionary selection pattern, structural and motif features. Phylogenetic analysis classified BnaSMXL genes into 4 distinct sub-clades representing clear orthologous relationships to their family members in Arabidopsis and rice. Conserved motif analysis indicated that the motif 16 mediating strigolactones(SLs) or karrikins(KARs) signaling was absent in SMXL3-5 genes. Orthologous gene pairs between Arabidopsis and 3 Brassica species were extracted, and 8 SMXL genes in Arabidopsis genome had 16, 16 and 31 corresponding genes in B. oleracea, B. rapa and rapeseed genomes respectively. Evolutionary selection pattern showed that most of SMXL genes had undergone stronger negative selection. BnaSMXLs expression showed diverse patterns in 10 tissues of both vegetative and reproductive organs. Subcellular localization analysis showed that BnaSMXL proteins were exclusively localized in nucleus.

Non-transcriptional regulatory activity of SMAX1 and SMXL2 mediates karrikin-regulated seedling response to red light in Arabidopsis

Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways.The transcriptional repressor proteins SUPPRESSOR OF MAX21(SMAX1),SMAX1-like2(SMXL2),and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or byinhibiting the activities of transcription factors.In this study,we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis.We discovered that SMAX1 and SMXL2 with mutations in their ethylene-responsefactor-associated amphiphilic repression(EAR)motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant.SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR4(PIF4)and PIF5 to enhance their protein stability by interacting with phytochrome B(phyB)and suppressing the association of phyB with PIF4 and PIF5.The karrikin-responsive genes were then identified by treatment with GR24ent-ssa,GR24 analog showing karrikin activity.Interestingly,INDOLE-3-ACETIC ACID INDUCIBLE 29(IAA29)expression was repressed by GR24^(ent-5D)streatment in a PIF4-and PIF5-dependent and EARindependent manner,whereas KARRIKIN UPREGULATED F-BOX 1(KUF1)expression was induced in a PIF4-and PIF5-independent and EAR-dependent manner.Furthermore,the non-transcriptional regulatory activity of SMAX1,which is independent of the EAR motif,had a global effect on gene expression.Taken together,these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.

The MAX2-KAI2 module promotes salicylic acid-mediated immune responses in Arabidopsis

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 MAX21/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 resistance 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 response.We measured the resistance of smaxl and smxl mutants,as well as the double,triple,and quadruple mutants with max2,which revealed that both the smax1 mutant and smx16/7/8 triple mutant rescue the low resistance phenotype of max2 and that SMAX1 accumulation diminishes resistance.The susceptibility of smax1D,containing a degradation-insensitive form of SMAX1,further confirmed the SMAX1 function in the resistance.The relationship between the accumulation 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 resistance against Pst,but KAR-induced resistance depended 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.

棉花SMXL基因家族的全基因组分析及表达分析

独脚金内酯(strigolactones,SLs)是一种新型植物激素,在植物生长发育中发挥重要作用.目前在棉花中对SL研究仍较少,探究SL影响棉花生长发育及纤维品质形成的功能和机制具有重要意义.SMXL(SUPPRESSOR OF MAX21-like)是独角金内酯信号通路的关键基因,充当SL信号转导的阻遏物,关于棉花SMXL基因的研究尚未见报道.本文以陆地棉、海岛棉、亚洲棉及雷蒙德氏棉全基因组为基础,运用生物信息学方法,根据SMXL蛋白序列结构域特征鉴定到16个GhSMXL基因、16个GbSMXL基因、8个GaSMXL基因和8个GrSMXL基因.系统发育分析发现SMXL分为4个亚家族:SMXL-Ⅰ(SMXL1,2),SMXL-Ⅱ(SMXL6,7,8),SMXL-Ⅲ(SMXL3)和SMXL-Ⅳ(SMXL4,5).对SMXL的进化特征分析发现,位于同一亚组间的SMXL成员具有相似的基因结构与蛋白结构.分析发现,片段复制是SMXL成员在棉花中扩张的主要方式.组织表达谱分析显示,在陆地棉中GhSMXL1-A,GhSMXL1-D,GhSMXL7-1-A,GhSMXL7-1-D,GhSMXL8-1-A,GhSMXL8-1-D在根、茎、叶、纤维及胚珠中优势表达;在亚洲棉中GaSMXL8-1,GaSMXL1,GaSMXL7在根、茎、叶和胚珠中优势表达.这些优势表达基因多数位于SMXL-Ⅰ,SMXL-Ⅱ亚家族,推测位于SMXL-Ⅰ,SMXL-Ⅱ亚家族中的多数基因可能是陆地棉或亚洲棉中在根、茎、叶和胚珠发育中发挥功能的关键基因.胁迫表达谱分析显示:SMXL-Ⅱ和SMXL-Ⅲ亚家族的基因(GhSMXL8-1-A,GhSMXL8-1-D,GhSMXL8-2-A,GhSMXL8-2-D,GhSMXL3-1-A,GhSMXL3-1-D,GhSMXL3-2-A,GhSMXL3-3-A和GhSMXL3-3-D)在盐、旱、低温、高温不同的胁迫模式下具有不同的响应方式,同一基因可能同时响应两种不同胁迫方式,例如GhSMXL8-1-A响应低温胁迫同时也响应盐胁迫,推测这些基因可能调控陆地棉非生物胁迫的响应.本研究为此后深入研究棉花SMXL基因功能奠定了基础.