Morphological and physiological studies on densely branched lateral roots triggered by localized phosphate in Sesbania cannabina

Densely branched lateral roots (DBLRs) in Sesbania cannabina are formed in response to patchily distributed phosphorus (P) in volcanic soils. Little attention has been paid to morphological and physiological responses of DBLRs. Here, we investigated the relation between plant growth and DBLR development, enzymatic activities involved in P acquisition, and the influence of arbuscular mycorrhizal fungi (AMF), which contribute to P uptake, to clarify the function of DBLRs. We investigated DBLR development induced by localized application of P fertilizer and we compared the activities of phosphoenolpyruvate carboxylase (PEPCase) and acid phosphatase (APase) between DBLRs and non‐DBLRs. Additionally, plants were grown with or without AMF to investigate the effect of AMF colonization on the numbers of DBLRs and plant P uptake, and we compared AMF colonization between DBLRs and non‐DBLR roots. Secondary to quaternary lateral DBLRs were produced after the primary lateral roots passed near P fertilizer. P_i content per DBLR increased as DBLRs developed, promoting higher shoot growth. Under P deficiency, PEPCase and APase activities increased in non‐DBLR, but were significantly lower in DBLRs in the same plants. AMF inoculation changed the root system architecture by significantly decreasing the number of DBLRs, and AMF colonization was lower in DBLRs than in non‐DBLRs. Our results indicate that DBLR formation is a P‐coacquisition strategy of S. cannabina grown in P‐deficient andosolic soil. Roots that form DBLR are clearly different from non‐DBLR roots in morphological and biochemical response and AMF symbiosis.     

抗精噁唑禾草灵耿氏硬草乙酰辅酶A羧化酶基因研究

为明确耿氏硬草抗性种群SD-23对乙酰辅酶A羧化酶(ACCase)抑制剂类除草剂的抗性水平及靶标抗性分子机理,采用整株水平测定法测定了SD-23种群对6种ACCase抑制剂类除草剂的抗性,扩增和比对了抗性和敏感种群间的ACCase基因序列,并测定了耿氏硬草种群SD-23对其他4种除草剂的敏感性。结果表明,SD-23种群对精噁唑禾草灵产生了高水平抗性,抗性倍数为12.7,对炔草酯和精吡氟禾草灵产生了低水平抗性,抗性倍数分别为5.2和4.5,对烯禾啶、烯草酮和唑啉草酯较敏感。与敏感种群SD-1相比,SD-23种群ACCase的CT区域第2096位甘氨酸突变为丙氨酸(Gly-2096-Ala);甲基二磺隆、啶磺草胺和异丙隆对抗性和敏感种群均有较好防效,其防效达86.7%以上,干重防效达77.4%以上。ACCase的Gly-2096-Ala突变第一次在耿氏硬草中被报道,该突变可能是导致SD-23种群对精噁唑禾草灵产生抗性的重要原因之一。     

MAPKs and acetyl-CoA are associated with Curvularia lunata pathogenicity and toxin production in maize

Mitogen-activated protein kinase (MAPK) cascades play an important role in extracellular signal transduction and are involved in the pathogenicity of fungal pathogens to host plants. In Curvularia lunata, the roles of two MAPK genes, Clk1 and Clm1, have already been studied. Clk1 is involved in conidia formation and pathogenicity, and Clm1 is closely related to pathogen cell wall formation and pathogenicity to maize leaves. In this study, a third C. lunata MAPK gene, Clh1, which is homologous to hog1, was successfully cloned. We found that a Clh1 deletion mutant had lower intracellular glycerol accumulation than the wild-type stain and was unable to grow normally under osmotic stress conditions. Furthermore, the deletion mutants of three C. lunata MAPK genes (Clk1, Clm1 and Clh1) had lower levels of acetyl-CoA, which is an important intermediate product in the synthesis of melanin and furan toxin, and down-regulated expression of pathogenicity-associated genes. Furthermore, pathogenicity and the ability to produce toxin were restored after adding acetyl-CoA to the culture medium, suggesting that acetyl-CoA is closely involved in the pathogen MAPK signaling pathway.     

黄瓜幼苗Rubisco与Rubisco活化酶对光强的响应

以津优3号幼苗为试材,研究弱光(LL:100 μmol· m-2·s-1)、亚弱光(SL:300 μmol·m-2·s-1)下黄瓜幼苗光合速率(Pn)、核酮糖-1,5-二磷酸羧化/加氧酶(Rubisco)、Rubisco活化酶(RCA)活性及其基因表达量的变化.结果表明,11d弱光处理后,黄瓜幼苗叶片的Pn、Rubis...     

橡胶树磷酸烯醇式丙酮酸羧化酶基因HbPPC1的克隆和表达分析

根据橡胶树磷酸烯醇式丙酮酸羧化酶(PEPC)基因的部分序列设计引物，运用RT-PCR和RACE方法获得其家族成员的1个全长cDNA，命名为HbPPC1，长度3 025 bp，包含5′-UTR 34 bp，3′-UTR 93 bp，开放阅读框2 898 bp，编码965个氨基酸。预测HbPPC1分子量为110.34 ku，理论等电点为6.09。HbPPC1具有C3型PEPC的结构特征，其N端第9~17位残基是可逆磷酸化的不变序列-X-X-SIDAQLR，C端倒数第4位残基为谷氨酰胺(Q)，第774位残基为丙氨酸(A)。HbPPC1与5条大戟科植物的PEPC序列(其中木薯2条、蓖麻2条、麻风树1条)的同源性达到95％。系统进化分析表明，HbPPC1与这5条序列聚在同一个进化支中。HbPPC1包含2个酶活性位点和7种类型的Motifs，二级结构以由α-螺旋和无规则卷曲为主。Real-time RT-PCR结果表明，HbPPC1在橡胶树胶乳、叶片、树皮和花中均表达，在胶乳中的表达量最高；胶乳HbPPC1的表达受乙烯利刺激影响，在乙烯利刺激4~72 h后胶乳HbPPC1表达明显下调，表明HbPPC1在胶乳pH值调控中起重要作用。本研究结果为HbPPC1的功能研究提供理论依据。     

田间条件下转玉米C4型PEPC基因小麦的光合生理特性

为了检验转PEPC基因小麦是否具有C₄光合生理特性，以转PEPC基因小麦和对照周麦19为试验材料，分别于抽穗期、开花期、花后第7天和花后第15天测定其单株旗叶的气体交换参数日变化，对净光合速率日变化进行单位日光合总量分析, 并且对净光合速率日变化与单株气孔导度、胞间CO₂浓度、蒸腾速率日变化的相关性进行了分析；在花后第15天测定其单株叶绿素荧光参数，并在成熟期调查了单株产量性状。与对照相比，转基因株系在4个测定时期的旗叶净光合速率明显提高，尤其在花后第15天，单位日光合总量较对照提高29.1%和23.3%，气孔导度和蒸腾速率均明显增加，胞间CO₂浓度降低；花后第15天12:00与8:00相比，转PEPC基因小麦的F_v/F_m、q_p、NPQ、Φ_PSII的变幅均小于对照；单茎重、千粒重、单穗重和收获指数较对照显著增加。以上结果表明，转PEPC基因小麦材料在田间条件下光合特性明显优于对照，且具有提高小麦产量水平的潜力。