OsNAC2通过ABA依赖途径负调控水稻的多种非生物胁迫反应

在植物感受外界环境变化和对各种胁迫产生应答反应的过程中,转录因子是必不可少的一个环节,但是其中很多重要的成员和功能还不清楚.OsNAC2是NAC转录因子家族的一个成员,它的表达受到ABA和几种非生物胁迫的强烈诱导,如干旱和高盐.通过构建OsNAC2的过表达和RNAi株系,连同野生型共同评价OsNAC2的生物学功能.在营养生长时期,与野生型相比,过表达株系对干旱和高盐更加敏感.相反地,RNAi株系则表现更好的干旱和高盐抗性.通过芯片数据分析,发现在OsNAC2过表达植株中,许多胁迫相关基因的表达量均下调.这些结果说明OsNAC2负调控水稻的非生物胁迫反应,并且可能是ABA依赖通路中的一个重要因子.     

干旱胁迫下甘蓝型油菜相关抗旱基因的表达分析

以抗旱性较强的甘蓝型油菜Holiday为材料,在开花初期对油菜进行干旱胁迫处理,采用RT-qPCR技术分析ABA2、BnSOS2、BnCS、CAM、CBF4、PIP1这6个油菜抗旱相关基因在干旱胁迫第1天、3天、5天、7天在根、茎、叶、花和青荚中的表达量.结果表明,干旱胁迫下,6个抗旱相关基因在油菜的不同器官中均出现了上调表达;在不同干旱胁迫下,各基因表达量呈现不同的变化趋势;在相同的器官中,各基因的表达量存在明显的不同,累积表达量表现为根中ABA2最大、CBF4最小,茎中CAM最大、CBF4最小,叶中PIP1最大、ABA2最小,花中CBF4最大、BnSOS2最小,青荚中BnCS最大,CBF4最小.说明植物在受到干旱胁迫时,不同的抗旱途径对干旱胁迫的响应程度是不同的;不同器官中各抗旱相关基因与胁迫时间的相关性分析表明,CAM基因在茎中的表达量、CBF4基因在花中的表达量与胁迫时间呈显著正相关.     

UV-B预处理对拟南芥uvr8-2突变体响应干旱胁迫的影响

以拟南芥uvr8-2突变体植株为材料,研究UV-B预处理对植株响应干旱胁迫的影响以及植物激素在此过程中的作用.实验结果表明:从形态观察到生理指标,UV-B预处理显著提高了拟南芥uvr8-2突变体的干旱适应性,与野生型Ler的结果一致;UV-B预处理显著提高了拟南芥uvr8-2突变体抗氧化酶SOD、POD、CAT活性,抗氧化酶基因POD和CAT的表达量,以及植物激素ABA、JA、SA的质量分数,降低了细胞膜受损程度.由此推测:UV-B预处理诱导uvr8-2植株的干旱适应性中存在一条不依赖于UVR8的信号转导途径,即通过增加植物逆境响应激素ABA、JA和SA的质量分数,调控抗氧化酶基因CAT和POD表达和增强抗氧化酶活性,从而缓解干旱胁迫下拟南芥的叶片萎焉、相对含水量下降等现象.     

MYB家族转录因子OsMYB84通过ABA信号通路参与盐胁迫响应

MYB家族是植物中最大的转录因子家族之一,功能广泛,这类蛋白在植物器官形态建成、次生代谢、激素代谢和信号途径起关键调控作用.从水稻中克隆R2R3-MYB家族转录因子OsMYB84,聚类分析结果表明OsMYB84为拟南芥MYB84同源基因,洋葱表皮亚细胞定位研究显示OsMYB84为核定位蛋白.器官表达谱和原位杂交分析实验显示OsMYB84在水稻叶枕、茎以及根中高表达.构建OsMYB84过表达体系,筛选出纯合株系.与野生型相比,OsMYB84转基因水稻的株高明显矮化,因此推测OsMYB84可能通过影响茎和叶枕处侧生分生组织进而改变株高.另一方面,激素和胁迫表达谱分析结果表明,OsMYB84受到ABA、高盐的显著诱导.同时,OsMYB84显著提高了转基因水稻的耐盐特性,减少细胞损伤并且也提高了转基因水稻种子对ABA的敏感性,这暗示着OsMYB84基因可能通过依赖ABA信号通路参与水稻盐胁迫应答反应.     

复苏植物牛耳草BhLEA2基因启动子的分离和基因表达模式研究

为研究干旱诱导的基因表达模式,利用Inverse-PCR和Tail-PCR的方法从复苏植物牛耳草（Boea hygrometrica（Bunge）R Br．）中扩增出胚胎发育晚期丰富蛋白编码基因BhLEA2的1215bp启动子序列,命名为PBhLEA2。构建了由PBhLEA2启动子引导GUS嵌合基因的植物表达载体pBhLEA2-GUS,并经农杆菌介导导入到烟草中,得到4株转基因烟草植株。GUS检测分析表明,该启动子可驱动GUS报告基因在转基因烟草的种子和刚萌发的小苗的子叶和胚轴中高效表达,在10-20d苗龄的植株中不表达,表现出一定的发育阶段和组织特异性。干旱、高盐胁迫及脱落酸（ABA）、乙烯和H2O2等信号分子可在不同程度上诱导GUS报告基因在20d苗龄的转基因植株的叶片中表达,但只有ABA可诱导其在根中表达,表明该启动子对BhLEA2基因表达的调控受环境信号影响。     

用差异显示技术分离空心莲子草抗旱相关基因

采用mRNA差异显示技术,分离空心莲子草在干旱胁迫1 d后差异表达的基因,获得139个基因片段.经过Reverse Northern检测,初步证实有两个片段受干旱诱导表达上调.对其中一个片断克隆测序并进行核甘酸序列比对,显示与其他基因同源性都很低,表明可能是新的基因.半定量PCR技术证实该基因受干旱诱导表达上调.     

水稻HD-Zip Ⅲ家族成员OsHox10的功能分析

为了探究HD-ZipⅢ家族成员之一OsHox10在水稻发育中的功能,构建了OsHox10的过量表达载体并获得了转基因株系,明确了OsHox10基因的表达模式和亚细胞定位,并初步了解它与植物激素及抗旱性的关系.表型观察发现,过量表达OsHox10能使水稻叶片出现不同程度的皱缩、卷曲,尤其是靠近叶鞘部分卷曲明显. OsHox10基因的组织特异性表达结果表明,OsHox10在水稻不同器官中都有表达,但主要在分裂旺盛的部位,如茎顶端分生组织及不同时期的幼穗中表达量较高.亚细胞定位结果表明,OsHox10定位于细胞质中或者细胞膜上.分析OsHox10在植物激素及干旱条件处理下的表达,结果发现,激素及干旱处理均能够诱导OsHox10基因的表达,表明OsHox10可能与水稻响应激素信号和干旱胁迫有关.     

干旱胁迫下蒙古沙冬青AmNAC1基因的表达差异及功能分析

测定蒙古沙冬青NAC家族成员的编码基因AmNAC1在干旱胁迫和外源ABA处理下的表达模式,通过转基因拟南芥在干旱胁迫下的表型分析,探究AmNAC1的功能和作用机理.结果显示:AmNAC1在蒙古沙冬青幼苗中受干旱以及外源ABA的诱导;超表达AmNAC1可以不同程度地提高转基因拟南芥对干旱胁迫的耐性,也可以提高转基因拟南芥离体叶片和幼苗在自然干燥期间的保水能力,但对其种子萌发期响应外源ABA的敏感性无明显影响.结果表明AmNAC1在植物响应和抵抗干旱胁迫中起重要调节作用.     

拟南芥At5g66070基因在ABA处理下的初步研究

本研究以拟南芥为实验材料,探索基因At5g66070在植物激素ABA处理条件下的相关生理功能.结果表明,在10μMABA处理下,该基因的表达量明显升高,表明该基因受到ABA的诱导.亚细胞定位发现AT5G66070定位在细胞核.通过DNA及RNA水平筛选鉴定At5g66070基因T-DNA插入纯合突变体,然后经根瘤农杆菌介导法进行遗传转化,筛选获得过表达转基因株系.表型分析发现经ABA处理后,突变体相对于野生型而言根长较短,表明突变体对ABA更为敏感.气孔关闭实验发现10μM ABA能诱导突变体气孔关闭,而野生型和过表达无显著影响.以上结果表明At5g66070在拟南芥的ABA胁迫响应中起负调控作用.     

小拟南芥激素相关基因及GH3.6的克隆与表达

植物激素是植物体内产生的一些微量的、能调节自身生理过程的有机化合物,生长素是一种重要的植物激素,在植物生长发育的过程中起着重要作用。为了探索激素相关基因在短命植物小拟南芥(Arabidopsis pumila)逆境适应过程中的作用,本研究基于小拟南芥响应高盐胁迫叶片转录组数据库,首先筛选出2156个激素相关基因,包括生长素、脱落酸、乙烯、水杨酸、茉莉酸、油菜素内酯、细胞分裂素及赤霉素相关的基因,其中生长素和脱落酸相关基因所占比例最多并且多为上调表达。进一步通过分层聚类(H-Cluster),K均值聚类(K-means Cluster)和密度聚类(SOM Cluster)分析持续上调的基因,发现一个编码吲哚乙酸酰胺合成酶的基因GRETCHEN HAGEN 3. 6(GH3. 6)在高盐胁迫过程中明显上调表达。采用RT-PCR克隆小拟南芥Ap GH3. 6基因,其开放阅读框长为1839 bp,编码612个氨基酸。系统进化分析表明,Ap GH3. 6与山"菜(Eutrema salsugineum) GH3. 6进化关系最近,属于同一进化分支。转录组数据分析表明在250 m M Na Cl下,Ap GH3. 6持续上调表达;实时荧光定量PCR分析表明Ap GH3. 6在小拟南芥各个组织中均有表达,但在花中表达量最高;高盐胁迫表达分析表明,随着胁迫时间增加,Ap GH3. 6表达量不断升高。为了进一步研究该基因的功能,构建了植物过量表达载体35S∶Ap GH3. 6并转化农杆菌GV3101。本研究为深入分析激素相关基因在小拟南芥响应盐胁迫中的功能机制奠定了基础。     

A silicon transporter in rice

Silicon is beneficial to plant growth and helps plants to overcome abiotic and biotic stresses by preventing lodging (falling over) and increasing resistance to pests and diseases, as well as other stresses. Silicon is essential for high and sustainable production of rice, but the molecular mechanism responsible for the uptake of silicon is unknown. Here we describe the Low silicon rice 1 (Lsi1) gene, which controls silicon accumulation in rice, a typical silicon-accumulating plant. This gene belongs to the aquaporin family and is constitutively expressed in the roots. Lsi1 is localized on the plasma membrane of the distal side of both exodermis and endodermis cells, where casparian strips are located. Suppression of Lsi1 expression resulted in reduced silicon uptake. Furthermore, expression of Lsi1 in Xenopus oocytes showed transport activity for silicon only. The identification of a silicon transporter provides both an insight into the silicon uptake system in plants, and a new strategy for producing crops with high resistance to multiple stresses by genetic modification of the root's silicon uptake capacity.     

硝普钠及其光解产物对日本晴水稻幼苗生长和5种激素标记基因表达的影响

以粳稻品种日本晴水稻为材料,检测硝普钠及其光解产物KNO_2、K_4Fe(CN)_6对幼苗生长的影响,并采用qRT-PCR技术检测了5种植物激素标记基因在经上述处理后在幼苗根中的表达水平.结果表明SNP能够显著抑制水稻幼苗的根长和株高;SNP对根生长的抑制主要是通过其光解产物K4Fe(CN)6实现的.SNP和K_4Fe(CN)_6处理都能够抑制生长素、细胞分裂素、脱落酸和赤霉素4种激素标志基因在水稻根中的表达,但是SNP处理可以抑制一氧化氮标志基因OsNOA1的表达,而K_4Fe(CN)_6则上调该基因的表达.     

水稻Os05g0442400基因启动子分析以及由Os05g0442400基因启动子引导GUS报告基因在转基因水稻中的表达

采用Plant CARE和PLACE软件分析预测水稻Os05g0442400基因启动子序列中可能存在的顺式作用元件.结果显示,在起始密码子ATG上游1500bp区域内,除了启动子基本的核心作用元件外,还存在一些与植物抵御非生物胁迫过程有关的作用元件、脱落酸应答元件、光诱导启动子作用元件、病原菌诱发因子作用元件,以及根特异性结合位点.采用根癌农杆菌介导法成功将Os05g0442400 promoter::gus构建导入"中花11"水稻.由不同组织部位GUS染液检测表明:在水稻苗期,内源Os05g0442400基因可能主要在根部表达;随着水稻生殖期的延续,水稻内源Os05g0442400基因在颖壳中的表达区域由上向下面积增大,并在抽穗后达到最大表达区域.这些结果可能与Os05g0442400基因启动子上分别存在根特异性结合位点和光诱导启动子作用元件具有一定的联系.     

Promoter of soybean early nodulin gene<Emphasis Type="Italic">enod2B</Emphasis> is induced by rhizobial Nod factors in transgenic rice

Nod factors, which are signaling molecules produced by Rhizobia, are the principal determinants of host specificity in Rhizobium-legume symbiosis. Nod factors can elicit a number of characteristic developmental responses in the roots of legumes, such as depolarization of the membrane potential in epidermal cells, specific expression of early nodulin genes and changes in the flux of calcium in root hairs, deformation of root hairs, cell division in the root cortex and formation of the nodule primordinm. Whether the rice plant can respond to signaling molecules (i.e. Nod factors) is an important question, as it could establish the potential for symbiotic nitrogen fixation in rice. The promoter of the soybean (Glycine max) early nodulin gene Gmenod2B fused to the β-glucuronidase (GUS) reporter gene was used as a molecular marker to explore whether Nod factors can be recognized by rice cells as signaling molecules. Transgenic rice plants harboring the chimeric gene Gmenod2BP-GUS were obtained via an Agrobacterium tumefaciens-mediated system. NodNGR factors produced by a broad-host-range Rhizobium strain NGR234(pA28) were used as probes to investigate the activity of the Gmenod2B promoter in rice. Our results showed that the early nodulin gene Gmenod2B promoter was induced by NodNGR factors in transgenic rice, and that it was specifically expressed in rice plant roots. Moreover, GUS gene expression driven by the Gmenod2B promoter in transgenic rice was regulated by nitrogen status. These findings indicated that rice possessed the ability to respond to Nod factor signals, and that this signal transduction system resulted in activation of the Gmenod2B promoter. Thus, we predict that the Nod-factor inducible nodulin expression system, which is similar to Rhizobium-legume symbiosis, may also exist in rice.     

Cloning and expression of putative ethylene receptor genes in soybean plant

Ethylene plays important roles in plant growth, development, and stress responses, and ethylene receptors have been identified and studied extensively in various plant species. Here we report the cloning of four ethylene receptor genes from soybean, i.e. GmETR1, GmERS1, GmETR2 and GmEIN4. Construction of the phylogenic tree showed that GmETR1 and GmERS1 belong to subfamily I whereas GmETR2 and GmEIN4 belong to subfamily II. The four ethylene receptor genes showed different tissue-specific expression patterns in roots, stems, leaves, cotyledons, flowers, pods and seeds of soybean. These genes were differentially regulated by various abiotic stresses and plant hormones. The possible roles of the four genes in soybean plant were also discussed.     

Cloning and expression of putative ethylene receptor genes in soybean plant

Ethylene plays important roles in plant growth, development, and stress responses, and ethylene receptors have been identified and studied extensively in various plant species. Here we report the cloning of four ethylene receptor genes from soybean, i.e. GmETR1, GmERS1, GmETR2 and GmEIN4. Construction of the phylogenic tree showed that GmETR1 and GmERS1 belong to subfamily I whereas GmETR2 and GmEIN4 belong to subfamily II. The four ethylene receptor genes showed different tissue-specific expression patterns in roots, stems, leaves, cotyledons, flowers, pods and seeds of soybean. These genes were differentially regulated by various abiotic stresses and plant hormones. The possible roles of the four genes in soybean plant were also discussed.     

The epigenetic involvement in plant hormone signaling

The biosynthesis and signaling of plant hormones play a critical role in almost all biological processes. It is well-documented that phytohormones cross-talk with each other. Epigenetic mechanisms were suggested to regulate expression of downstream targets in hormone signaling pathways that help implement hormone functions. This new layer of complexities that integrate epigenetic information such as DNA methylation, chromatin remodeling, histone modification, microRNAs and siRNAs with plant hormone signaling and regulations of gene expression, has been gradually revealed. In this short review, the author tries to assemble recent progress to establish a molecular linkage between these two large and momentum research fields and also to help readers digest the literature.     

Ideal root architecture for phosphorus acquisition of plants under water and phosphorus coupled stresses: From simulation to application

Under water and phosphorus (P) coupled stresses, root architecture may be related to P acquisition efficiency of plants. Understanding the relationship between root architecture and P acquisition efficiency may provide basic information for improving P acquisition efficiency of plants. In the present study, we quantitatively described the effects of root architecture on P acquisition efficiency by computer simulation together with controlled biological experiments so as to determine an ideal root architecture for efficient P acquisition under water and P coupled stresses. Our results indicate that under given soil water conditions, the ideal root architecture for P acquisition efficiency of a tap root plant (as represented by common bean) is an 搖mbrella-shape?root system whose basal roots tend to be shallow in the P-rich topsoil and tap roots tend to be deep for water in the subsoil. Meanwhile, the ideal root architecture for a fibrous root plant (as represented by upland rice) is a beard-shape?root system with the moderately dispersed yet uniformly distributed adventitious and lateral roots so as to keep most roots in the topsoil for P and a few roots in the subsoil for water.     

白桦BpTCP8基因生物信息学及表达特性分析

【目的】通过研究白桦BpTCP8基因的序列特征及其在不同组织部位、激素处理与胁迫应答中的表达特性,为揭示BpTCP8在白桦生长发育中的功能提供依据。【方法】利用生物信息学方法对BpTCP8基因进行分析,采用实时荧光定量 PCR 技术分析BpTCP8基因在不同组织部位、激素处理与胁迫应答中的表达特性。【结果】生物信息学分析发现,BpTCP8含有TCP家族高度保守的bHLH结构域;qRT-PCR分析结果表明,白桦BpTCP8在发育和衰老初期的叶片中表达量高,并在深裂型叶片、顶芽、木质部、韧皮部中都上调表达。在激素(GA₃、ME-JA、ABA)与非生物胁迫(PEG、NaCl、CdCl₂、NaHCO₃)处理下,BpTCP8都对其产生了相应的应答。【结论】BpTCP8基因可能参与到了白桦叶片成熟、叶型、顶芽、木质部和韧皮部的生长过程中;该基因在GA₃、JA处理中呈现正调控的应答模式,并且可能通过ABA信号途径影响植物抗旱,耐盐、碱、重金属胁迫等。     

An efflux transporter of silicon in rice

Silicon is an important nutrient for the optimal growth and sustainable production of rice. Rice accumulates up to 10% silicon in the shoot, and this high accumulation is required to protect the plant from multiple abiotic and biotic stresses. A gene, Lsi1, that encodes a silicon influx transporter has been identified in rice. Here we describe a previously uncharacterized gene, low silicon rice 2 (Lsi2), which has no similarity to Lsi1. This gene is constitutively expressed in the roots. The protein encoded by this gene is localized, like Lsi1, on the plasma membrane of cells in both the exodermis and the endodermis, but in contrast to Lsi1, which is localized on the distal side, Lsi2 is localized on the proximal side of the same cells. Expression of Lsi2 in Xenopus oocytes did not result in influx transport activity for silicon, but preloading of the oocytes with silicon resulted in a release of silicon, indicating that Lsi2 is a silicon efflux transporter. The identification of this silicon transporter revealed a unique mechanism of nutrient transport in plants: having an influx transporter on one side and an efflux transporter on the other side of the cell to permit the effective transcellular transport of the nutrients.