A novel calcium-dependent protein kinase gene from Populus euphratica, confers both drought and cold stress tolerance

Populus species are the most important timber trees over the Northern hemisphere. Most of them are cold- and drought-sensitive except the Populus euphratica Oliv. Here, a calcium-dependent protein kinase (CDPK) gene cloned from P. euphratica, designated as PeCPK10, was rapidly induced by salt, cold, and drought stresses. The protein encoded by PeCPK10 was localized within the nucleus and cytosol, which may be important for its specific regulation in cellular functions. To elucidate the physiological functions of PeCPK10, we generated transgenic Arabidopsis plants overexpressing PeCPK10. The results showed that PeCPK10-transgenic lines experienced better growth than vector control plants when treated with drought. Stronger abscisic acid-induced promotion of stomatal closing has been showed in transgenic lines. Particularly, overexpression of PeCPK10 showed enhanced freezing tolerance. Constitutive expression of PeCPK10 enhanced the expression of several abscisic acid-responsive genes and multiple abiotic stress-responsive genes such as RD29B and COR15A. Accordingly, a positive regulator responsive to cold and drought stresses in P. euphratica is proposed.     

Identification of microRNAs and their targets from Populus euphratica

Populus euphratica is an ideal model system for research into the abiotic stress resistance research of woody plants. Although microRNAs have been found in poplars and have been shown to have diverse biological functions, a majority of them are genus- or specie-specific and few microRNAs have been found in P. euphratica to date. In this study, microRNA cloning and computational expressed sequence tag analysis were used to identify 72 putative miRNA sequences in P. euphratica. These sequences could be classified into 21 families, 12 of which were novel, increasing the number of known poplar microRNA families from 42 to 54. Expression analysis indicated that five P. euphratica microRNAs were induced by dehydration stress. Bioinformatics prediction showed that the 130 target genes are involved in development, resistance to stress, and other cellular processes. These results suggest several roles for miRNAs in the regulatory networks associated with the abiotic stress resistance of tree species.     

基于遥感图像处理技术胡杨叶气孔密度的估算及其生态意义

拟利用遥感图像处理技术--面向对象分类,计算胡杨叶片气孔密度,采用面向对象分类的专业软件eCognition对气孔图像进行多尺度分割,将生成的分类图像导入ArcGIS中计算气孔密度,最后用R语言编写代码进行批处理。研究结果显示:该方法用于计算叶片气孔的密度精度高;18个样点胡杨气孔密度存在着较大的差异,从76.7 个/mm²到139.4 个/mm²不等,其平均密度为105 个/mm²;随着干旱胁迫加强,气孔密度表现下降上升再下降的趋势。     

塔里木河下游地下水埋深对胡杨气体交换和叶绿素荧光的影响

为了分析干旱环境下地下水埋深变化对胡杨(Populus euphratica oliv.)光合作用的影响,对塔里木河下游3个地下水埋深(4.91,6.93m和8.44m)环境下胡杨叶片的气体交换日变化、光响应曲线、PN-C_i曲线以及叶绿素荧光特性等进行了比较研究。研究结果表明:当地下水埋深从4.91m增加到6.93m和8.44m,胡杨光合速率(P_N)(10:00),初始荧光(F₀)、最大荧光(F_m)、以及PSⅡ实际光化学效率(Ω_PSⅡ)、电子传递速率(ETR)、非光化学猝灭系数(NPQ)和正午叶水势(Ψ_midday)等都发生了明显变化,其中胡杨NPQ增加了109% 127%,Ω_PSⅡ,ETR和Ψ_midday分别减小了24% 29%,17% 22%和31.6% 45.6%,表明胡杨受到的干旱胁迫程度在增加;而当地下水埋深在6.93 8.44m之间时,上述参数无显著变化,表明胡杨很可能处于相同干旱胁迫程度;并且在地下水埋深4.91 8.44m范围内,最大光化学效率(F_v/F_m),表观量子效率(φ),Rubisco羧化速率(V_cmax), 等参数都未发生明显变化,表明即使地下水埋深增加到8.44m,此时的干旱胁迫程度也未超过胡杨的耐受能力,其光合能力也未受到不可逆转的伤害。     

不同林龄胡杨克隆繁殖根系分布特征及其构型

以中龄林和成熟林胡杨为研究对象,采用挖剖面和根窗的方法,研究胡杨繁殖根系分布、根系构型,以及胡杨根蘖与繁殖根系构型之间的关系。结果表明:(1)细根(d<2 mm)的根长密度、根表面积密度,随深度增加呈现指数函数分布;(2)中龄林细根的根长密度、根表面积密度在0—90 cm各层都是显著大于成熟林的对应指标(P<0.05),成熟林的中等粗根(5 mm0.05),且两种林龄的一级侧根数、分枝角度亦无显著差异(P>0.05);(5)对比两种林龄不同根序上的根蘖芽发现,二级根上不定芽个数均是同组一级根上不定芽个数的3—4倍;基于以上对胡杨根系的功能权衡的分析,得出:细根对胡杨根系构型有重要的影响,在胡杨根系功能权衡中扮演重要角色。     

黑河下游绿洲胡杨生长状况与叶生态特征

选择黑河下游额济纳绿洲为研究区,以优势物种胡杨(Populus euphratica Oliv.)为研究对象。在2009年和2010年对研究区胡杨的生长状况、叶生态特征和生境进行了调查。调查结果表明:胡杨受水分胁迫的程度增强,生长态势变差,其枯枝比由2.45%增加到81.00%,其比叶面积由11.84 m2/kg减少到5.35 m2/kg。叶气孔密度变化很大,最小值为105(个/mm2),最大值为218(个/mm2),平均值为158.4(个/mm2),随着地下水埋深的增加,叶气孔密度先减少后增加之后再显著减少(P0.05),呈三次函数关系。研究得出枯枝比能够反映胡杨分布区地下水的变化状况,是林相描述比较重要的指标,比叶面积和叶气孔密度能够指示胡杨种群环境变化。研究结果可为荒漠河岸林恢复和生态输水效应评价提供科学依据。     

Identification and characterization of salt-responsive microRNAs in Populus tomentosa by high-throughput sequencing

Salt is one of the main environmental factors limiting plant growth and a better understanding of mechanisms of salt stress would aid efforts to bolster plant salt tolerance. MicroRNAs are well known for their important regulatory roles in response to abiotic stress in plants. In this study, high-throughput sequencing was employed to identify miRNAs in Populus tomentosa plantlets treated or not with salt (200 mM for 10 h). We found 141 conserved miRNAs belonging to 31 families, 29 non-conserved but previously-known miRNAs belonging to 26 families, and 17 novel miRNAs. Under salt stress, 19 miRNAs belonging to seven conserved miRNA families were significantly downregulated, and two miRNAs belonging to two conserved miRNA families were upregulated. Of seven non-conserved miRNAs with significantly altered expression, five were downregulated and two were upregulated. Furthermore, eight miRNAs were validated by qRT-PCR and their dynamic differential expressions were analyzed. In addition, 269 target genes of identified miRNAs were predicted and categorized by function. These results provide new insights into salt-responsive miRNAs in Populus.