Functional analyses of the maize CKS2 gene promoter in response to abiotic stresses and hormones

In our previous research, we showed that the cyclin-dependent kinase regulatory subunit (CKS2) in maize (Zea mays L.) was induced by water deficit and cold stress. To elucidate its expression patterns under adversity, we isolated and characterized its promoter (PZmCKS2). A series of PZmCKS2-deletion derivatives, P0–P3, from the translation start code (?1,455, ?999, ?367, and ?3 bp) was fused to the β-glucuronidase (GUS) reporter gene, and each deletion construct was analyzed by Agrobacterium-mediated steady transformation into Arabidopsis. Leaves were then subjected to dehydration, cold, abscisic acid (ABA), salicylic acid (SA), and methyl jasmonic acid (MeJA). Sequence analysis showed that several stress-related cis-acting elements (MBS, CE3, TGA element, and ABRE) were located within the promoter. Deletion analysis of the promoter, PZmCKS2, suggested that the ?999 bp promoter region was required for the highest basal expression of GUS, and the ?367 bp sequence was the minimal promoter for ZmCKS2 activation by low temperature, ABA, and MeJA. The cis-acting element ABRE was necessary for promoter activation by exogenous ABA.     

GmPOI gene encoding a Pollen_Ole_e_I conserved domain is involved in response of soybean to various stresses

In the previous research, a novel gene GmPOI (GenBank acc. No. HM235775) encoding a Pollen_Ole_e_I conserved domain was identified in roots of soybean drought resistant cv. Jindou 23. In the present study, GmPOI was cloned and functionally characterized. Real-time quantitative PCR indicated that the expression of GmPOI was induced by drought, cold, salt and abscisic acid in wild-type soybean. The soybean plants overexpressing GmPOI showed higher tolerance to drought stress than wild types. We concluded that GmPOI is probably a novel gene that is involved in the response to various stresses in soybean.     

菜用大豆CIPK基因对逆境胁迫及激素的响应特征

CIPK(calcineurin B-like-interacting protein kinase)是一类丝氨酸/苏氨酸蛋白激酶,在植物响应逆境胁迫和激素信号转导中发挥重要作用。本研究利用大豆基因组数据库,在全基因组水平鉴定获得52个CIPK蛋白激酶。蛋白比对分析发现所有Gm CIPK含有高度保守特征性的N端激酶区、连接区和C端调控区。系统进化树分析发现大豆Gm CIPK与拟南芥、水稻CIPK分类一致,分为4个亚家族,且每个亚家族含有3个不同物种的成员,表明Gm CIPK基因的分化早于物种的分化。启动子分析表明,多数Gm CIPK基因的启动子区含有逆境和激素应答元件。组织表达分析发现,Gm CIPK基因呈现多样化的组织表达特性。进一步选取组织表达量相对较高的14个Gm CIPK进行荧光定量PCR分析,结果表明这些菜用大豆CIPK基因在不同程度上均受高温、干旱、高盐胁迫以及ABA、ACC、SA、Me JA激素的诱导表达。采用蛋白同源比对和蛋白互作在线数据库对拟南芥及大豆同源CIPK蛋白激酶与其他蛋白的互作关系进行了预测分析,发现17对同源CIPK与其他蛋白(激酶、磷酸酶、转录因子等)存在互作。本研究为菜用大豆CIPK基因的功能研究与利用奠定了基础。     

Partial suppression of gene encoding proline dehydrogenase enhances plant tolerance to various abiotic stresses

The role of gene of proline dehydrogenase (PDH) in the maintenance of stress tolerance was investigated using the model transgenic plants of tobacco (Nicotiana tabacum L.) carrying an antisense suppressor of PDH gene (a fragment of Arabidopsis PDH gene under the control of cauliflower mosaic virus 35S promoter in antisense orientation) and notable for a low activity of PDH and elevated content of proline. The progeny of transgenic plants belonging to the 5th generation (T₅) with partially suppressed PDH activity was more resistant to various types of stress as compared with the control plants of tobacco, cv. Petit Havana SR-1 (SR1). The seedlings of transgenic lines cultured in Petri dishes on agar media supplemented with stress agents were resistant to high NaCl concentrations (200–300 mM) and water deficit simulated by an increased agar content in the medium (14 g/l) as compared to the control seedlings of cv. SR1. Juvenile plants of transgenic lines grown in pots filled with a mixture of vermiculite and perlite also manifested the higher resistance to water deficit and low temperatures (2°C and −2°C) than the control plants. Thus, the partial PDH suppression correlated with an increase in nonspecific resistance to different types of abiotic stress: salinity, water deficit, and low temperatures. Such transgenic lines of tobacco are promising genetic models for thorough investigation of molecular mechanisms of stress resistance in plants.     

Isolation and functional analysis of cotton universal stress protein promoter in response to phytohormones and abiotic stresses

The 949 bp promoter fragment upstream from the translation initiation site of the GUSP gene encoding a universal stress protein was isolated from the genomic DNA of Gossypium arboreum. Some putative cis-acting elements involved in stress responses including E-box, ABRE, DPBF-box, and MYB-core elements were found in the promoter region. In an Agrobacterium-mediated transient expression assay, strong activation of the GUSP full promoter region occurred in tobacco leaves following dehydration, abscisic acid, salt, heavy metal, gibberellic acid and dark treatments. Deletion analysis of the promoter revealed that the dehydration, abscisic acid and salt responses were affected by the deletion between −208 and −949 bp and showed 2–4-fold induction. However, in response to dark, gibberellic acid and heavy metals the induction was only 2-fold. These findings further our understanding of the regulation of GUSP expression. This is an important study as no report of this universal stress protein promoter is available in literature.     

A rice (Oryza sativa L.) MAP kinase gene, OsMAPK44, is involved in response to abiotic stresses

We have isolated and characterized a putative rice MAPK gene (designated OsMAPK44) encoding for a protein of 593 amino acids that has the MAPK family signature and phosphorylation activation motif, TDY. Alignment of the predicted amino acid sequences of OsMAPK44 showed high homology with other rice MAPKs. Under normal conditions, the OsMAPK44 gene is highly expressed in root tissues, but relatively less in leaf and stem tissues of the japonica type rice plant (O. sativa L. Donggin). mRNA expression of the gene is highly inducible by salt and drought treatment, but not by cold treatment. Moreover, the mRNA level of the OsMAPK44 is up-regulated by exogenously applied Abscisic acid (ABA) and H₂O₂. When we compared the OsMAPK44 gene expression level between a salt sensitive indica cultivar (IR64) and a salt resistant indica cultivar (Pokkali), they showed some difference in expression kinetics with the salt treatment. OsMAPK44 gene expression in Pokkali was slightly up-regulated within 30 min and then disappeared rapidly, while IR64 maintained its expression for 1 h following down-regulation. Under the salinity stress, OsMAPK44 overexpression transgenic rice plants showed less damage and greater ratio of potassium and sodium than OsMAPK44 suppressed transgenic lines did, suggesting that OsMAPK44 may have a role to prevent damages due to working for favorable ion balance in the presence of salinity.     

Expression of stress gene networks in tomato lines susceptible and resistant to Tomato yellow leaf curl virus in response to abiotic stresses.

The defense response to several abiotic stresses has been compared in two tomato inbred lines issued from the same breeding program, one susceptible and the other resistant to Tomato yellow leaf curl virus (TYLCV) infection. The level of oxidative burst and the amounts of key regulatory stress proteins: pathogenesis-related proteins (PRs), heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPKs) were appraised following treatments with NaCl, H(2)O(2), and ethanol. Significant differences in the response of the two tomato genotypes to these stresses have been found for HSPs and MAPKs patterns at the level of down-regulation but not activation. The higher abundance of HSPs and MAPKs in tomatoes resistant to TYLCV could result in enhanced defense capacity against abiotic stresses.     

Cytokinin action in response to abiotic and biotic stresses in plants

The phytohormone cytokinin was originally discovered as a regulator of cell division. Later, it was described to be involved in regulating numerous processes in plant growth and development including meristem activity, tissue patterning, and organ size. More recently, diverse functions for cytokinin in the response to abiotic and biotic stresses have been reported. Cytokinin is required for the defence against high light stress and to protect plants from a novel type of abiotic stress caused by an altered photoperiod. Additionally, cytokinin has a role in the response to temperature, drought, osmotic, salt, and nutrient stress. Similarly, the full response to certain plant pathogens and herbivores requires a functional cytokinin signalling pathway. Conversely, different types of stress impact cytokinin homeostasis. The diverse functions of cytokinin in responses to stress and crosstalk with other hormones are described. Its emerging roles as a priming agent and as a regulator of growth‐defence trade‐offs are discussed.     

Isolation of an osmotin-like protein gene from strawberry and analysis of the response of this gene to abiotic stresses

A strawberry genomic clone containing an osmotin-like protein (OLP) gene, designated FaOLP2, was isolated and sequenced. FaOLP2 is predicted to encode a precursor protein of 229 amino acid residues, and its sequence shares high degrees of homology with a number of other OLPs. Genomic DNA hybridization analysis indicated that FaOLP2 represents a multi-gene family. The expression of FaOP2 in different strawberry organs was analyzed using real-time PCR. The results showed that FaOLP2 expressed at different levels in leaves, crowns, roots, green fruits and ripe red fruits. In addition, the expression of FaOLP2 under different abiotic stresses was analyzed at different time points. All of the three tested abiotic stimuli, abscisic acid, salicylic acid and mechanical wounding, triggered a significant induction of FaOLP2 within 2-6h post-treatment. Moreover, FaOLP2 was more prominently induced by salicylic acid than by abscisic acid or mechanical wounding. The positive responses of FaOLP2 to the three abiotic stimuli suggested that strawberry FaOLP2 may help to protect against osmotic-related environmental stresses and that it may also be involved in plant defense system against pathogens.     

Brassinosteroids and their role in response of plants to abiotic stresses

Brassinosteroids (BRs) are polyhydroxylated steroidal plant hormones that play pivotal role in the regulation of various plant growth and development processes. BR biosynthetic or signaling mutants clearly indicate that these plant steroids are essential for regulating a variety of physiological processes including cellular expansion and proliferation, vascular differentiation, male fertility, timing senescence, and leaf development. Moreover, BRs regulate the expression of hundreds of genes, affect the activity of numerous metabolic pathways, and help to control overall developmental programs leading to morphogenesis. On the other hand, the potential application of BRs in agriculture to improve growth and yield under various stress conditions including drought, salinity, extreme temperatures, and heavy metal (Cd, Cu, Al, and Ni) toxicity, is of immense significance as these stresses severely hamper the normal metabolism of plants. Keeping in mind the multifaceted role of BRs, an attempt has been made to cover the various aspects mediated by BRs particularly under stress conditions and a possible mechanism of action of BRs has also been suggested.     

Expression analysis of five maize MAP kinase genes in response to various abiotic stresses and signal molecules

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in eukaryotes. Plant MAPK cascades are complicated networks and play vital roles in signal transduction induced by biotic and abiotic stresses. In this paper, expression patterns of MAPKs in maize roots treated with low-temperature, osmotic stresses, wounding, plant hormones and UV-C irradiation were investigated. Semi-quantitative RT-PCR reveals that the expression of MAPKs in maize roots which treated with low-temperature in light or in low light are inducible. The expression patterns of MAPKs in maize roots with treatments of CaCl₂, SA, GA and wounding are approximately the same. A detailed time course experiment shows that the expression patterns of ZmSIMK are different with treatments of PEG and NaCl, respectively. These results suggest that the expression patterns of MAPKs are complicated and the signal pathways are interlaced into a network in maize roots.     

Regulation of the rose Rh-PIP2;1 promoter by hormones and abiotic stresses in Arabidopsis

Our previous work has indicated that an ethylene-responsive aquaporin gene, Rh-PIP2;1, played an important role in the epidermal cell expansion of rose petals. In this work, we isolated an 896 bp promoter sequence of the Rh-PIP2;1 and found that the promoter was rare in plants, occurring with an Inr motif, but without a TATA box. In transgenic Arabidopsis harboring the Rh-PIP2;1 promoter::GUS construct, the activity of Rh-PIP2;1 promoter was found to be developmental-dependent in almost all of the tested organs, and was particularly active in organs that were rapidly expanding, and in tissues with high water flux capacity. Moreover, the promoter activity was inhibited by ACC, ABA, NaCl, and cold in the roots of 3 or 6-day-old plants, and was increased by GA₃ and mannitol in the rosettes of 9 or 12-day-old plants. Deleting the fragment from −886 to −828 resulted in nearly complete disappearance of the promoter activity in roots, and a substantial decrease in the leaves, hypocotyls and floral organs. Taken together, our results indicated that the Rh-PIP2;1 promoter responded to hormones and abiotic stresses in a developmental- and spatial-dependent manner, and the −886 to −828 region was crucial for the activity of the Rh-PIP2;1 promoter. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Y. Li and Z. Wu contributed to this work equally.