Specific Interaction with Cardiolipin Triggers Functional Activation of Dynamin-Related Protein 1

Dynamin-Related Protein 1 (Drp1), a large GTPase of the dynamin superfamily, is required for mitochondrial fission in healthy and apoptotic cells. Drp1 activation is a complex process that involves translocation from the cytosol to the mitochondrial outer membrane (MOM) and assembly into rings/spirals at the MOM, leading to membrane constriction/division. Similar to dynamins, Drp1 contains GTPase (G), bundle signaling element (BSE) and stalk domains. However, instead of the lipid–interacting Pleckstrin Homology (PH) domain present in the dynamins, Drp1 contains the so-called B insert or variable domain that has been suggested to play an important role in Drp1 regulation. Different proteins have been implicated in Drp1 recruitment to the MOM, although how MOM-localized Drp1 acquires its fully functional status remains poorly understood. We found that Drp1 can interact with pure lipid bilayers enriched in the mitochondrion-specific phospholipid cardiolipin (CL). Building on our previous study, we now explore the specificity and functional consequences of this interaction. We show that a four lysine module located within the B insert of Drp1 interacts preferentially with CL over other anionic lipids. This interaction dramatically enhances Drp1 oligomerization and assembly-stimulated GTP hydrolysis. Our results add significantly to a growing body of evidence indicating that CL is an important regulator of many essential mitochondrial functions.     

Differential Expression of Specific Proteins during In Vitro Tomato Organogenesis1

The cotyledons of tomato (Lycopersicon esculentum L., cv. Jia Fen-10) seedlings were induced to produce calli and regenerate plants via organogenesis. Utilizing this system, the composition and content of stage-specific proteins associated with organogenesis were analyzed. Moreover, a comparison of the protein composition and content between embryogenic and nonembryogenic calli was conducted. The SDS-PAGE results and laser densitometric scanning maps showed that there were different specific proteins expressed at different stages. Among them, six proteins (61, 54, 38, 37, 35, and 23 kD) were associated with the morphogenesis of organs, and two proteins (39 and 24 kD) were related to the morphogenesis of calli. Although no distinctive difference in protein components of embryogenic calli was noted, there were different trends of changes, both for the content of the proteins 39 and 24 kD, and for the content of the total proteins, at different developmental stages of embryogenic calli. The results obtained from the embryogenic and nonembryogenic calli indicated that these two materials were distinct in the protein components as well as in its content; for example, the protein 54 kD was detected in nonembryogenic but not in embryogenic calli. The total protein content in nonembryogenic calli was lower than that in the embryogenic calli.     

Integrin Signaling: Cytoskeletal Complexes,MAP Kinase Activation,and Regulation of Gene Expression

Members of the integrin family of adhesion receptors mediate interactions of cells with the extracellular matrix. Besides their role in tissue morphogenesis by anchorage of cells to basement membranes and migration along extracellular matrix proteins, integrins are thought to play a key role in mediating the control of gene expression by the extracellular matrix. Studies over the past 10 years have shown that integrin-mediated cell adhesion can trigger signal transduction cascades involving translocation of proteins and protein tyrosine phosphorylation events. In this review, we discuss approaches used in our lab to study early events in integrin signalling as well as further downstream changes.     

Nano-TiO2 Improve the Photosynthesis of Tomato Leaves under Mild Heat Stress

Nano-TiO₂ has been reported to promote photosynthesis in some crops; however, the mechanism behind this action remains unknown. In this research, the effects of nano-TiO₂ on leaf photosynthesis under mild heat stress were investigated. Results showed that the net photosynthetic rate, conductance to H₂O, and transpiration rate of tomato leaves increased after application of an appropriate concentration of nano-TiO₂. Nano-TiO₂ also significantly decreased the minimum chlorophyll fluorescence and relative electron transport in leaves. Under mild heat stress, Nano-TiO₂ increased regulated photosystem II (PS II) energy dissipation and decreased non-regulated PS II energy dissipation. These results indicate that nano-TiO₂ plays a positive role in promoting photosynthesis in tomato leaves under mild heat stress.     

番茄 SlDP1 基因的克隆、生物信息学及表达特性分析简

DP基因属于DP/E2F转录因子家族,其编码的蛋白是E2F蛋白的二聚化分子伴侣,可能参与调控细胞周期、DNA复制、生长、分化、凋亡等多种细胞进程。根据SGN数据库登录的番茄序列,通过RT-PCR方法从野生型番茄中克隆了一个DP基因,命名为SlDP1。生物信息学预测,SlDP1蛋白定位于细胞核,具有保守的DNA结合域、二聚化区域和C-末端及多个磷酸化位点。蛋白质二级结构预测SlDP1蛋白含51.50%的环状结构,34.55%的α螺旋和2.66%的β折叠。荧光定量PCR分析外源激素对野生型番茄SlDP1基因表达量的影响,发现该基因受外源性乙烯前体ACC的诱导。对环境因子应答的RT-PCR结果表明,在伤害和盐处理的叶中该基因表达不受诱导,而盐处理的根中该基因表达量提高。SlDP1基因表达模式分析表明,该基因在根、花、萼片及成熟时期果实中表达量较高。这些结果为进一步研究SlDP1基因在番茄生长发育过程的功能奠定了基础。     

番茄钙依赖性蛋白激酶基因LeCPK2在热(光)胁迫中的功能鉴定

钙依赖性蛋白激酶(calcium-dependent protein kinases,CDPKs or CPKs)作为一类钙感知蛋白在植物的生长发育和胁迫应答中起着重要的作用.LeCPK2 (GenBank accession No.:GQ205414)是我们从番茄中分离的第3个CDPK基因,前期研究表明LeCPK2可能在植物热胁迫应答中发挥作用.为了进一步研究其在热胁迫中的功能,我们通过电子克隆的方法分离了LeCPK2的启动子序列,并通过LeCPK2过表达烟草分析其在高温胁迫中的潜在的功能.生物信息学分析显示,LeCPK2启动子中包含5个热响应元件,和前期试验结果一致.野生型植株在受到热胁迫后,对光更为敏感,强光照下植株叶片发生萎蔫,而强光本身不会对未受热胁迫的健康植株造成伤害.LeCPK2转基因植株热、光胁迫后不会出现受害表型.以上研究表明,LeCPK2在植物的热胁迫应答中发挥重要作用,能够有效保护植株免受高温胁迫的损害,是一个优秀的耐热(光)基因.本研究将为揭示番茄LeCPK2遗传功能及对其开发利用奠定基础.     

番茄LeEIL1基因的克隆分析及表达载体构建

采用RT-PCR方法从番茄果实cDNA中成功克隆了番茄LeEIL1基因,并测序验证序列正确;经数据库检索等生物信息学分析方法,对番茄LeEIL1蛋白质与拟南芥、烟草、水稻、香石竹等的EIN3/EILs蛋白质序列进行了同源性分析,初步确定了番茄LeEIL1上的DNA结合功能域及其结合激活位点.并构建了LeEIL1的酵母表达工程茵pPIC9k-EIL1/KM71,为该基因的功能研究奠定了基础.     

番茄LeNHX1基因植物过量表达载体的构建及表达分析

从番茄幼苗中提取RNA,根据NCBI中番茄LeNHX1基因序列设计引物,通过RT-PCR获得了番茄LeNHX1基因的cDNA序列,包含一个1 605 bp的开放阅读框,编码534个氨基酸。将cDNA序列连接到植物过量表达载体PBI121上,对所获得的重组质粒进行双酶切鉴定,结果表明,植物过量表达载体PBI121-LeNHX1已构建成功。半定量RT-PCR结果表明LeNHX1基因在根、茎和叶中均表达,盐、低温和脱落酸的诱导能提高LeNHX1基因的表达量,推测番茄LeNHX1基因在逆境应答中可能起着重要作用。