Female self-incompatibility type in heterostylous Primula is determined by the brassinosteroid-inactivating cytochrome P450 CYP734A50

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H_2O_2和MAPK介导油菜素内酯诱导番茄抗氧化防护酶SOD和CAT的信号途径

本文以番茄为材料,研究H2O2和MAPK在BR诱导的抗氧化防护系统中的作用。结果表明,外源BR提高抗氧化防护酶SOD和CAT活性;而这种诱导机制被H2O2产生抑制剂二苯基碘（DPI）和MEK1/2专一抑制剂PD98059阻断。进一步研究发现：BR能够诱导细胞质外体H2O2的产生,这种诱导被PD98059抑制;BR能够活化一种49kDaMAPK,这种活化被DPI抑制。本研究结果证实细胞质外体H2O2和MAPK候选激酶（49kDaMAPK）信号参与BR诱导的抗氧化防酶途径,且两者之间存在交互作用。     

Somatic Embryogenesis Receptor Kinases Control Root Development Mainly via Brassinosteroid-Independent Actions in Arabidopsis thaliana

Brassinosteroids(BRs),a group of plant steroidal hormones,play critical roles in many aspects of plant growth and development.Previous studies showed that BRI1-mediated BR signaling regulates cell division and differentiation during Arabidopsis root development via interplaying with auxin and other phytohormones.Arabidopsis somatic embryogenesis receptor-like kinases(SERKs),as co-receptors of BRI1,were found to play a fundamental role in an early activation step of BR signaling pathway.Here we report a novel function of SERKs in regulating Arabidopsis root development.Genetic analyses indicated that SERKs control root growth mainly via a BR-independent pathway.Although BR signaling pathway is completely disrupted in the serk1 bak1 bkk1 triple mutant,the root growth of the triple mutant is much severely damaged than the BR deficiency or signaling null mutants.More detailed analyses indicated that the triple mutant exhibited drastically reduced expression of a number of genes critical to polar auxin transport,cell cycle,endodermis development and root meristem differentiation,which were not observed in null BR biosynthesis mutant cpd and null BR signaling mutant bri1-701.     

外源EBR和NO信号对低温胁迫下玉米种胚抗氧化系统和低温响应基因表达的影响

以玉米主栽品种先玉335为试材,研究24-表油菜素内酯(EBR)对低温胁迫下玉米种胚抗氧化能力和低温响应基因表达的影响.结果表明:EBR浸种处理后,玉米种子活力指数和早期幼苗生长显著提高,种胚中超氧自由基(O2(-))含量明显降低,抗氧化酶(包括超氧化物歧化酶SOD、过氧化物酶POD、过氧化氢酶CAT和谷胱甘肽还原酶GR等)活性和非酶类抗氧化物质谷胱甘肽GSH及脯氨酸含量升高,同时促进一氧化氮(NO)的累积,而使用NO清除剂c-PTIO和NO合成酶抑制剂L-NAME处理后,种胚中CAT、POD和脯氨酸含量有所下降,但是外源NO可提高种胚中CAT、POD和脯氨酸的含量,表明EBR诱导的玉米种胚抗氧化能力增加是通过NO介导的.低温胁迫诱导玉米幼胚中P5CS1、CBF1、CBF3和COR15a等基因的表达,EBR处理基因表达进一步提高,而c-PTIO和L-NAME处理基因表达降低;NO供体SNP则提高了这些基因的表达,这表明EBR可能通过NO途径调控低温响应基因的表达.可见,外源EBR可通过NO途径增强玉米种胚抗氧化能力和调控低温响应基因的表达,进而提高低温胁迫的耐受性.