植物凝集素类受体蛋白激酶研究进展

自然界中植物的生长发育受到各种环境变化的影响。为了响应外界各种环境条件,植物演化出一系列识别和传递环境信号的蛋白分子,其中比较典型的是植物细胞质膜上的类受体蛋白激酶(RLKs)。凝集素类受体蛋白激酶(LecRLKs)是类受体蛋白激酶家族中的一个亚族,它主要包含3个结构域:细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域。根据细胞外凝集素结构域的不同,LecRLKs可分为3种不同类型:L、G和C型。近年来,研究表明LecRLKs在植物生物/非生物胁迫和发育调控中发挥非常重要的作用。该文综述了植物凝集素类受体蛋白激酶的研究历史、结构特点、分类以及生物学功能,并重点阐述凝集素类受体蛋白激酶在植物生物/非生物胁迫响应和调控发育方面的功能。对不同类型和不同功能的植物凝集素类受体蛋白激酶进行阐述将有利于对该类蛋白开展功能研究,并为作物改良提供有益借鉴。     

植物凝集素类受体激酶参与非生物胁迫响应的研究进展

植物在生长发育过程中会受到各种胁迫因子的影响,非生物胁迫是其中极其重要的一类。类受体激酶(receptor-like kinases, RLKs)是植物中广泛存在的一类蛋白,能够快速有效地对胁迫因子作出响应,最终引起一系列生物效应。凝集素类受体激酶(lectin receptor-like kinases, LecRLKs)是RLKs的一个亚族,其具有细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域三个结构域。根据细胞外凝集素结构域的不同可分为L、G和C三种不同类型。近年来,大量的研究表明植物凝集素类受体激酶在非生物胁迫响应中发挥重要作用。LecRLKs通过识别非生物胁迫相关的信号分子,激活下游的信号通路,如MAPK通路、ROS通路、钙信号通路等,调节基因表达和蛋白质翻译以增强植物的抗逆性。该文概述了植物凝集素类受体激酶的结构特征及其分类,并系统综述了LecRLKs在盐胁迫、低温胁迫、干旱胁迫、机械损伤和植物激素等非生物胁迫响应中的功能和作用机制,同时也对LecRLKs的未来研究方向作出了展望。该文不仅为深入了解植物凝集素类受体激酶参与非生物胁迫响应的功能提供了参考,而且为利用LecRLKs进行作物抗逆育种改良提供了理论依据。     

Plant acyl-CoA-binding proteins: An emerging family involved in plant development and stress responses

Acyl-CoA-binding protein (ACBP) was first identified in mammals as a neuropeptide, and was demonstrated to belong to an important house-keeping protein family that extends across eukaryotes and some prokaryotes. In plants, the Arabidopsis ACBP family consists of six AtACBPs (AtACBP1 to AtACBP6), and has been investigated using gene knock-out mutants and overexpression lines. Herein, recent findings on the AtACBPs are examined to provide an insight on their functions in various plant developmental processes, such as embryo and seed development, seed dormancy and germination, seedling development and cuticle formation, as well as their roles under various environmental stresses. The significance of the AtACBPs in acyl-CoA/lipid metabolism, with focus on their interaction with long to very-long-chain (VLC) acyl-CoA esters and their potential role in the formation of lipid droplets in seeds and vegetative tissues are discussed. In addition, recent findings on the rice ACBP family are presented. The similarities and differences between ACBPs from Arabidopsis and rice, that represent eudicot and monocot model plants, respectively, are analyzed and the evolution of plant ACBPs by phylogenetic analysis reviewed. Finally, we propose potential uses of plant ACBPs in phytoremediation and in agriculture related to the improvement of environmental stress tolerance and seed oil production.     

Genome-wide expression analysis of rice ABC transporter family across spatio-temporal samples and in response to abiotic stresses

Although the super family of ATP-binding cassette (ABC) proteins plays key roles in the physiology and development of plants, the functions of members of this interesting family mostly remain to be clarified, especially in crop plants. Thus, systematic analysis of this family in rice (Oryza sativa), a major model crop plant, will be helpful in the design of effective strategies for functional analysis. Phylogenomic analysis that integrates anatomy and stress meta-profiling data based on a large collection of rice Affymetrix array data into the phylogenic context provides useful clues into the functions for each of the ABC transporter family members in rice. Using anatomy data, we identified 17 root-preferred and 16-shoot preferred genes at the vegetative stage, and 3 pollen, 2 embryo, 2 ovary, 2 endosperm, and 1 anther-preferred gene at the reproductive stage. The stress data revealed significant up-regulation or down-regulation of 47 genes under heavy metal treatment, 16 genes under nutrient deficient conditions, and 51 genes under abiotic stress conditions. Of these, we confirmed the differential expression patterns of 14 genes in root samples exposed to drought stress using quantitative real-time PCR. Network analysis using RiceNet suggests a functional gene network involving nine rice ABC transporters that are differentially regulated by drought stress in root, further enhancing the prediction of biological function. Our analysis provides a molecular basis for the study of diverse biological phenomena mediated by the ABC family in rice and will contribute to the enhancement of crop yield and stress tolerance.     

One gene member of the ADP-ribosylation factor family is heat-inducible and enhances seed germination in <Emphasis Type="Italic">Nicotiana tabacum</Emphasis>

ADP ribosylation factors (ARFs), one group within the Ras superfamily of GTP-binding proteins, are ubiquitous within the eukaryotic kingdom. The functions of ARFs are extensive, and include regulatory roles in vesicular transportation, lipid metabolism, and microtubule dynamics, and the cellular processes related to these roles. Most ARFs have been identified from mammalian species and yeast; although little is known about the functional importance of ARFs in plants, it seems to be equally diverse and significant. We have been working on plant responses under heat stress, and showed that heat-shock can induce seed germination (Koo et al. in Plant Physiol 167:1030–1038, 2015). In the present study, we report nine ARF gene family members from tobacco (Nicotiana tabacum), all belonging to the same group (Class 1) in the phylogenetic analysis. One family member, NtARF1, was induced under high-temperature stress. To elucidate the biological function of NtARF1, we generated transgenic tobacco plants overexpressing NtARF1 and the seeds of these transgenic tobacco plants germinated earlier than the seeds of non-transgenic tobacco plants. We also classified ARF family genes in plant species through systematic genomic DNA sequence data-mining, focusing on the fully sequenced and extensively annotated genomes of Arabidopsis thaliana, Brachypodium distachyon, Medicago truncatula, Mimulus guttatus, Nicotiana benthamiana, Setaria italica, Solanum lycopercisum, and Solanum tuberosum, and of some major crops including rice, soybean, corn, and tobacco. The Class 1 of our phylogenetics analysis comprised the highest number of ARFs among the four groups obtained for all plant species analyzed, especially for crop plant species.     

Functional analysis of receptor-like kinases in monocots and dicots

Receptor-like kinases (RLKs) are signaling proteins that feature an extracellular domain connected via a transmembrane domain to a cytoplasmic kinase. This architecture indicates that RLKs perceive external signals, transducing them into the cell. In plants, RLKs were first implicated in the regulation of development, in pathogen responses, and in recognition events. RLKs comprise a major gene family in plants, with more than 600 encoded in the Arabidopsis genome and more than 1100 found in rice genomes. The greater number of RLKs in rice is mostly attributable to expansions in the clades that are involved in pathogen responses. Recent functional studies in both monocots and dicots continue to identify individual RLKs that have similar developmental and abiotic stress roles. Analysis of closely related RLKs reveals that family members might have overlapping roles but can also possess distinct functions.     

Comprehensive Analysis of Wall-Associated Kinase Genes and Their Expression Under Abiotic and Biotic Stress in Chinese Cabbage (Brassica rapa ssp. pekinensis)

The wall-associated kinase (WAK) gene family, a subfamily of the receptor-like kinase (RLK) gene family, is associated with the cell wall in plants, and has vital functions in cell expansion, pathogen resistance, and heavy metal stress tolerance because of their roles of the extracellular environment sensors to trigger intracellular signals in Arabidopsis. In the present study, 96 Chinese cabbage (Brassica rapa ssp. pekinensis) BrWAK gene family members were identified from the B. rapa genome using a reiterative database search and manual confirmation. The protein domain characterization, gene structure analysis, and phylogenetic analysis of the BrWAKs classified them into three gene groups. Comparative genomic analysis between WAK genes from Chinese cabbage and Arabidopsis revealed that the BrWAK genes have undergone the gene expansion and deletion events during evolution. Furthermore, the conserved motifs in the kinase domains of the WAK proteins and eukaryotic protein kinase family proteins were compared and some non-RD kinase proteins among the BrWAKs were identified. Ultimately, expression analysis of BrWAK genes in six tissues and under various stress conditions revealed that some tissue-specific WAK genes might function in callus cell growth and reproduction process; Bra012273, Bra016426, Bra016427, and Bra025882 might be involved in downy mildew resistance and high humidity stress; Bra012273, Bra025882, and Bra025883 might be responded to drought and heat stress. Taken together, this research was identified and classified the WAK gene family in Chinese cabbage and provided valuable resources to explore the potential roles of BrWAK genes in plant development and stress responses.

     

OsSDIR1 overexpression greatly improves drought tolerance in transgenic rice

Recent genomic and genetic analyses based on Arabidopsis suggest that ubiquitination plays crucial roles in the plant response to abiotic stress and the phytohormone abscisic acid (ABA). However, few such studies have been reported in rice as a monocotyledonous model plant. Taking advantage of strategies in biochemistry, molecular cell biology and genetics, the RING-finger containing E3 ligase OsSDIR1 (Oryza sativa SALT-AND DROUGHT-INDUCED RING FINGER 1) was found to be a candidate drought tolerance gene for engineering of crop plants. The expression of OsSDIR1 was detected in all tissues of rice and up-regulated by drought and NaCl, but not by ABA. In vitro ubiquitination assays demonstrated that OsSDIR1 is a functional E3 ubiquitin ligase and that the RING finger region is required for its activity. OsSDIR1 could complement the drought sensitive phenotype of the sdir1 mutant and overexpressing transgenic Arabidopsis were more sensitive to ABA, indicating that the OsSDIR1 gene is a functional ortholog of SDIR1. Upon drought treatment, the OsSDIR1-transgenic rice showed strong drought tolerance compared to control plants. Analysis of the stomata aperture revealed that there were more closed stomatal pores in transgenic plants than those of control plants. This result was also confirmed by the water loss assay and leaf related water content (RWC) measurements during drought treatment. Thus, we demonstrated that monocot- and dicot- SDIR1s are conserved yet have diverse functions.     

乌拉尔图小麦NAC转录因子的筛选与分析

NAC是植物特有的具有多种功能的一类转录因子,广泛参与植物的生长发育,器官建成及抗逆境胁迫等反应.目前有关NAC转录因子的研究主要针对模式植物(如拟南芥和水稻),而在小麦中的研究相对较少.本文利用生物信息学方法,获得乌拉尔图小麦(Triticum urartu)NAC转录因子家族基因的全长序列,并对其进化关系,生物学功能,染色体定位以及基因复制等进行预测与分析,同时利用荧光定量PCR验证相关转录因子在非生物胁迫下的表达模式.结果显示,共筛选得到87个乌拉尔图小麦全长NAC转录因子,通过进化树分析将其分为7个亚族,其中39个NAC 转录因子被定位在7条染色体上.通过基因复制分析发现,有5对NAC转录因子基因发生了复制.进一步通过荧光定量验证4个NAC转录因子在非生物胁迫下的表达模式,发现4个转录因子均受不同胁迫而上调表达.     

Ancient signals: comparative genomics of plant MAPK and MAPKK gene families

MAPK signal transduction modules play crucial roles in regulating many biological processes in plants, and their components are encoded by highly conserved genes. The recent availability of genome sequences for rice and poplar now makes it possible to examine how well the previously described Arabidopsis MAPK and MAPKK gene family structures represent the broader evolutionary situation in plants, and analysis of gene expression data for MPK and MKK genes in all three species allows further refinement of those families, based on functionality. The Arabidopsis MAPK nomenclature appears sufficiently robust to allow it to be usefully extended to other well-characterized plant systems.