Kinetin Treatment Research Articles

Expression analysis of nuclear W2-containing homologs of eukaryotic initiation factors in rice

The W2 domain is a conserved domain found firstly at the C-terminus of several translation initiation factors, but its roles are unknown. Here we identified three W2 genes in rice (Oryza sativa L.) which were located to the nucleus. The expression profiles of the three genes in response to phytohormones and abiotic stresses were also analyzed. OsW2-1 expression was mainly affected by two classes of phytohormones, including abscisic acid and cytokinin, and some abiotic stresses such as dark, drought and hypersaline, while both OsW2-2 and OsW2-3 expression levels were down-regulated by 2,4-dichloro-phenoxyacetic acid treatment. Besides, OsW2-2 under chilling stress, and OsW2-3 under 3-indolebutyric acid, kinetin and salt treatments, also showed slight transcription reduction. Our results first suggest that the three W2 genes function in phytohormone signaling pathways, and OsW2-1 also interrelated with the resistance to abiotic stresses in rice. It implies that the homologs of translation initiation factors in nuclei have different functions from those in the cytoplasm in eukaryotic cells.

Effects of the exogenous application of auxin and cytokinin on carbohydrate accumulation in grains of rice under salt stress

Phytohormones, such as auxin and cytokinin, are known to be involved in the regulation of plant responses to salinity stress and counteract the adverse effect of stress conditions. This work investigated the effects of the exogenous spraying of indole-3-acetic acid (IAA) and kinetin (KIN) during the reproductive phase on grain yield by examining the 1000-grain weight and filled-grain percentage as well as the changes in starch, total soluble sugars, sucrose, glucose and fructose concentrations in the grains of two rice cultivars under salt stress. The results indicated that the applied IAA and KIN led to an increased grain yield, 1000-grain weight and filled-grain percentage for both rice cultivars under salt stress. The storage starch content in the grain of the salt-sensitive cultivar was more than that in the salt-tolerant cultivar under IAA application compared with KIN, whereas a decrease in the total soluble sugar content was observed with both IAA and KIN treatments, in comparison to the non-hormone treatment. Interestingly, this study showed that IAA led to a much higher increase in the sucrose content in grain, as compared to the KIN. Furthermore, this experiment suggests that glucose and fructose may play important roles during salt stress because there were clearly higher concentrations of these sugars in the grain of the stressed cultivars under IAA and KIN application: it appears that their accumulation was the earliest response detected during the grain-filling period in rice. Finally, this work indicated that an increase in the rice grain yield, 1000-grain weight and filled-grain percentage are associated with an increase in the contents of starch, sucrose, glucose and fructose in grain caused by the application of IAA and KIN.

Micropropagation of the plantlets derived from seeds in the genus Acorus (A. calamus and A. gramineus)

The genus Acorus is a perennial hydrophyte used as a medicinal and aromatic plant. Acorus calamus and A. gramineus were cultured for in vitro investigation of growth rate, shoot formation and root formation on the media containing different kinds and concentrations of plant growth regulators. In A. calamus and A. gramineus, the seeds were germinated and the germination rate was almost 100%. Then, the seedlings were subcultured for the experiment on the MS medium containing 3% (w/v) sucrose and 0.8% (w/v) agar at different kinds and concentrations of plant growth regulators, auxins and cytokinins. The best shooting rate was obtained with about 100% on MS media containing BA (6-benzyl amino purine) or TDZ (N-phenyl-N′-[(1,2,3-thidiazol-5-yl) urea]). The number of developed shoots was significantly increased at 4 mg·L−1 BA with 5.4 shoots or 1 mg·L−1 TDZ with 11.0 shoots than control with 0.1 shoots in A. calamus. The A. gramineus showed slow growth rate and low shoot proliferation rate than A. calamus in general. In A. gramineus, the shoot formation was best in 4 mg·L−1 BA with 2.7 shoots or 1 mg·L−1 TDZ with 3.9 shoots than control with 0.9 shoots, respectively. Kinetin treatments brought 100% rooting rate, which were higher than that of BA and TDZ. Root formation was the best on the media containing 1 mg·L−1 NAA and 0.5 mg·L−1 NAA in A. calamus and A. gramineus, respectively. The plantlets were transferred to the greenhouse and survival rate was 95% after acclimatization.

Synergistic effect of kinetin and spermine on some physiological aspects of seawater stressed Vigna sinensis plants

The effect of kinetin, spermine and their combination on growth vigor, photosynthetic pigments, some metabolites, some enzymes, polyamines and productivity of salt-stressed Vigna sinensis plants was investigated. Salt stress reduced all evaluated growth criteria and yield components of used plants. Chlorophyll (CHL (a, b, carotenoids, carbohydrates, protein, spermidine and spermine level as well as and amylase activity were also decreased in response to salinity. On the other hand, proline, K +, Na + and putrescine concentration, and peroxidase activity were increased in the salt-stressed plants. Exogenous application of kinetin and spermine mitigated the deleterious effects of salinity stress on growth and yield of the used plants. Conversely, the combined treatment of kinetin and spermine induced additional reduction in growth and yield of the stressed plants, and the effect appeared to be constitutive. The protective effect of kinetin and spermine on V. sinensis plants appeared mainly due to the enhancement effect of these growth regulators on chlorophylls and protein content and polyamines titer.

RESPONSES OF SOME ENZYMES AND KEY GROWTH PARAMETERS OF SALT-STRESSED MAIZE PLANTS TO FOLIAR AND SEED APPLICATIONS OF KINETIN AND INDOLE ACETIC ACID

The study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) applied as seed treatment or sprayed on leaves of salinity stressed plants. Five -week old maize (Zea mays L. cv. ‘DK 647 F1’) plants were grown in pots containing peat and perlite in 1:1 (v/v) mixture. Different treatments used were: 1) control (nutrient solution alone), 2) salt stress [100 mM sodium chloride (NaCl)], 3) 100 mM NaCl and 1 mM kinetin (KIN), 4) 100 mM NaCl and 2 mM KIN, 5) 100 mM NaCl and 1 mM indole acetic acid (IAA), 6) 100 mM NaCl and 2 mM IAA, 7) 100 mM NaCl and 25 mg L−1 KIN and 8) 100 mM NaCl and 25 mg L−1 IAA. In treatments 7 and 8 application was to the seeds, for treatments 3-6 it was applied to foliage. The seeds were soaked in KIN or IAA solution for 12 h. Salt stress reduced the total dry matter, chlorophyll content, and relative water content (RWC), but increased proline accumulation, activities of superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC. 1.11.1.7), catalase (CAT; EC. 1.11.1.6) and polyphenol oxidase (PPO; 1.10.3.1) and electrolyte leakage. Both foliar applications of KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the above mentioned physiological parameters. However, seed treatments with KIN or IAA did not improve salinity tolerance in maize plants. Furthermore, foliar application or seed treatments with KIN and IAA reduced the activities of antioxidant enzymes in the salt stressed-plants. Salt stress lowered some macronutrient concentrations [calcium (Ca) and potassium (K) in leaves and roots, phosphorus (P) in roots] but foliar application of both KIN and IAA increased Ca in both leaves and roots and P in leaves. Foliar application of IAA increased K concentrations in leaves of the salt-stressed plants. Foliar application of KIN and IAA, especially at 2 mM concentration, counteracted some of the adverse effects of NaCl salinity by causing the accumulation of proline and essential inorganic nutrients as well as by maintaining membrane permeability.

Effect of foliar applied kinetin and indole acetic acid on maize plants grown under saline conditions

This study examined the effects of kinetin (KIN) and indoleacetic acid (IAA) sprayed on the leaves of salinity- stressed maize (Zea mays L. cv., DK 647 F1) plants grown in field conditions. Salt stress was created by adding 100 mM NaCl to the irrigation water through a drip irrigation system during the irrigation schedule. Kinetin (KIN), indole acetic acid (IAA), and their combinations were sprayed foliarly. Salt stress (S) reduced the total dry matter, grain yield, chlorophyll content, and relative water content (RWC), but increased electrolyte leakage and proline accumulation in the maize plants. Foliar applications of both KIN and IAA treatments overcame to variable extents the adverse effects of NaCl stress on the earlier mentioned physiological parameters. However, the combination of KIN plus IAA did not improve salinity tolerance in maize plants. Salt stress increased Na + concentration, and reduced those of Ca 2+ and K + in the leaves of maize plants. Foliar application of both KIN and IAA significantly reduced Na + concentration and increased those of Ca 2+ and K + . Foliar application of KIN and IAA, especially at 2 mM, counteracted some of the salt induced adverse effects by enhancing essential inorganic nutrients as well as by maintaining membrane permeability.

Modulation of aberrant NF1 pre-mRNA splicing by kinetin treatment

Neurofibromatosis type 1 is one of the most common neurocutaneous autosomal dominant disorders. It is caused by mutations in the neurofibromatosis type 1 (NF1) gene and approximately 30-40% of them affect the correct splicing of NF1 pre-mRNA. In this report, we evaluate the effect of five different drugs, previously found to modify splicing in several genetic disorders, on the splicing of mutated NF1 alleles. For this purpose, cell lines derived from patients bearing 19 different NF1-splicing defects were used. Our results showed that kinetin partially corrects the splicing defect in four of the studied mutations (c.910C>T, c.3113G>A, c.6724C>T and c.6791dupA). Our study is a valuable contribution to the field because it identifies new exon-skipping events that can be reversed by kinetin treatment and provides new information about kinetin splicing modulation. However, owing to the nature of mutations in our patients, kinetin treatment could not be used as a therapeutic agent in these cases.

Detached-Leaf Method for Propagating Puccinia coronata and Assessing Crown Rust Resistance in Oat.

The crown rust pathogen Puccinia coronata is an obligate biotroph with wind-disseminated propagules and numerous races. These characteristics make propagation of single-race cultures difficult. Genetic studies using single races in field and greenhouse environments are also problematic because pure cultures can easily become contaminated. In this study, we developed an isolated propagation system for P. coronata and tested its ability to assess host resistance. Oat (Avena sativa) leaf sections (10 cm each) were harvested, disinfested, and suspended in sterile plastic boxes by enclosing 3.5-cm linear sections of each leaf end between 4% agar blocks amended with various chemical constituents. The exposed sections (approximately 3 cm) were inoculated with P. coronata urediniospores suspended in water. Boxes were sealed and incubated in a lighted growth cabinet until the pathogen sporulated. Viable spores were produced on leaves in all treatments, whereas 6-benzylaminopurine (BAP) and kinetin treatments sustained the leaves longer and yielded the most viable spores. Based on these data, the BAP treatment was adopted and used for additional studies. Detached leaves of differential oat cultivars produced the same reactions as whole plants screened under standard conditions in a growth chamber. The proposed detached-leaf system should be useful for the propagation of numerous single-race cultures of P. coronata as well as evaluation of host resistance under highly controlled conditions.

Changes in photosynthetic apparatus of mustard (Sinapis alba) cotyledons following cycloheximide and kinetin treatments

Biochemical and accompanying structural characteristics of the photosynthetic process were studied in mustard seedlings cultivated on medium with increasing concentrations of cycloheximide alone as well as in combination with various kinetin concentrations. After 7 days of cultivation the contents of total chlorophyll, carotenoids and content of Rubisco in mustard cotyledons were determined. The content of chlorophyll pigments and carotenoids decreased in dependence of cycloheximide concentration. Following antibiotic treatment the content of both Rubisco subunits markedly decreased. In addition cycloheximide caused disturbance in mesophyll organization and chloroplast ultrastructure. Kinetin applied with cycloheximide increased the amount of photosynthetic pigments as well as of Rubisco, compared to the cycloheximide alone. In the seedlings treated with cycloheximide+kinetin the structure of leaf mesophyll and chloroplast membrane system was similar to control. Our results indicate that kinetin diminished the negative effects of cycloheximide on photosynthetic pigments and Rubisco as well as on the structural traits of the cotyledons.

Hormonal regulation of tiller dynamics in differentially-tillering rice cultivars

Tiller number can contribute significantly to yield potential of rice, but little knowledge is available on hormonal regulation of tillering and tiller dynamics. In the present study, Indole-3-acetic acid (IAA), kinetin (6-furfuryl amino purine) and Gibberellic acid (GA3) treatments have been applied at the early tillering stage to two rice cultivars that contrast for tiller number. The responses of the hormones were studied on growth, development, grain yield, senescence patterns, assimilate concentration of the panicle and ethylene production in different classes of tillers. The leaf area, panicle grain number, fertility percentage and grain yield of tillers were higher in the low-tillering cultivar than that of high-tillering cultivar; the treatment of kinetin was more effective in the latter than in the former. High ethylene production was responsible for reduction of growth duration and grain yield of the tillers. Kinetin application reduced ethylene production of the late-tillers significantly for the benefit of grain yield.

Plastid‐membrane‐associated polyamines and thylakoid transglutaminases during etioplast‐to‐chloroplast transformation stimulated by kinetin

The amounts of polyamines (PAs) bound to etioplast membranes varied during chloroplast development in cucumber cotyledons (Cucumis sativus L. cv. Racibór). Putrescine (PU) and spermidine (SD) levels increased in the early greening stage (6 h of light exposure) but decreased in the late greening stage (24 h) in the thylakoid‐enriched fraction. In the highly enriched PSIIα fraction, the trend of changes in the amount of bound PAs was different: levels of SD and spermine (SM) increased in the late stage. In both fractions, their levels were additionally increased by kinetin treatment. In the presence of exogenous protein transglutaminase (TGase) substrate (N′,N′‐dimethylcasein) and 5 mM Ca2+, kinetin initially caused a marked increase in thylakoid transglutaminase (ThylTGase) activity (6 h), followed by a decrease at the end of greening. The radiometric assay showed that PU and SM binding to thylakoid proteins was very low, while SD binding was seven to eight times higher. Kinetin increased SD conjugation in the early greening stage by about 36%. When chloroplast membranes were fully organized, ThylTGase activity decreased. In etioplast membranes and during the early greening stage, the 77‐kDa and 30‐kDa bands were mainly immunodetected with antibodies raised against the animal TGase, which were in general slightly stronger for kinetin‐treated than the control samples. At the end of greening, the level of 77‐kDa ThylTGase dramatically decreased. ThylTGase activity was found to be Ca2+ dependent. PAs conjugated via ThylTGase, in addition to the PAs bound by all possible types of linkage, could represent an important component of the mechanism of stimulation of etioplast‐to‐chloroplast transformation by kinetin.

EFFECT OF NITROGEN AND KINETIN ON THE GROWTH OF PLUM SEEDLINGS

This experiment was conducted out Nineveh research station during 2001-2002 season to study the effect of four levels of nitrogen fertilizer (0, 10, 20 and 30kg N/donum) and four concentrations of kinetin (0, 50, 100 and 150 ppm) and their interaction on the growth of one year old of plum (Prunus myroblane Ehrh.) seedlings. A factorial experiment with three replications was carried out in a randomized complete block design (RCBD), each replicate was consist of 30 seedlings. Data Obtained of this research was tested by using Duncan Multiple range test at 5% level, the important results of this study could be summarized as following: The Most of nitrogen fertilizer treatments significant increase all characters of the vegetative and root growth of the plum seedlings (stem length, stem diameters, dry weight of vegetative system) and roots, leaves contents of nitrogen and Chlorophyll. The addition of kinetin treatments as caused a significant increase in stem diameter, nitrogen concentration in the leaves and total chlorophyll, but there is no significant increases in stem length, dry weigh of vegetative growth and roots. The interaction treatments between nitrogen and kinetin affected significantly in most of the vegetative characters of the growth, dry weight of roots, nitrogen content in leaves, total chlorophyll concentration of leaves. The best treatments was 30kg N/donum + zero mg/L kinetin in stem length 30kg N/donum + 190 mg/L kinetin in stem diameter, nitrogen concentration in leaves total chlorophyll content ,30Kg N/donum + 100 mg/L kinetin in dry weight vegetative growth .

Exogenous cytokinin treatment maintains cyclin homeostasis in rice seedlings that show changes of cyclin expression when the photoperiod is rapidly changed

Cyclin is a fundamental regulator of the plant cell cycle. Five different types of cyclin genes (the A-, B-, C-, D-, and H-types) have been reported in Oryza sativa. However, except for Os;cycA1;1, Os;cycB2;1, and Os;cycB2;2, the mechanisms of expression of these cyclin genes have not yet been studied. The interactions of cyclins with cytokinin, an important trigger for cell cycle regulation, have also not been well studied. Here we used semi-quantitative RT-PCR in rice seedlings to analyze the effect of cytokinin on photomorphogenesis and the expression of six cyclin genes. Fifteen-day-old seedlings were grown in a 16/8 h light/dark cycle and then transferred to either constant light or constant dark. The expression of all the cyclin genes tested, except the C-type, decreased after 1 hour in the dark, but did not change after transfer to the light or when kinetin was added to the medium. Similarly, seedlings grown in the dark had decreased expression of the cyclin genes, except Os;cycB2;2, after transfer to the light, a decrease that was prevented by kinetin treatment. Thus, exogenous cytokinin plays an important role in maintaining homeostasis of cyclin gene expression following rapid changes of photoperiod.

Influence of arbuscular mycorrhizal fungi and kinetin on the response of mungbean plants to irrigation with seawater

Increasing use of saline water in irrigation can markedly change the physical and chemical properties of soil. An experiment was carried out to investigate the interaction between the mycorrhizal fungus Glomus clarum, isolated from a saline soil, and kinetin on the growth and physiology of mungbean plants irrigated with different dilutions of seawater (0, 10, 20, and 30%). The growth, chlorophyll concentration and sugar content of mycorrhizal plants was greater than that of non-mycorrhizal plants under all conditions (with or without seawater). The dry weight of both mycorrhizal and non-mycorrhizal mungbean plants irrigated with 10% seawater was significantly increased by treatment with kinetin. The mycorrhizal symbiosis increased root:shoot dry weight ratio, concentrations of N, P, K, Ca and Mg, plant height, protein content, nitrogen or phosphorus-use efficiencies, and root nitrogenase, acid or alkaline phosphatase activities of seawater-irrigated mungbean plants, with little or no effect of kinetin. Kinetin treatment generally decreased chlorophyll concentration and sugar content in mycorrhizal plants as well as Na/N, Na/P Na/K, Na/Ca and Na/Mg ratios. Root colonization by G. clarum was increased by irrigation with seawater, and kinetin had no consistent effect on fungal development in roots. This study provides evidence that arbuscular mycorrhiza can be much more effective than kinetin applications in protecting mungbean plants against the detrimental effects of salt water.

Cloning and expression analysis of 2-on-2 hemoglobin from soybean

Hemoglobins (Hbs) are heme proteins found in all five kingdoms of living organisms. In plants, three different classes of Hbs have been identified-nonsymbiotic Hbs from diverse species, symbiotic Hbs from nitrogen-fixing plants, and so-called 2-on-2 Hbs. Here, we report the cloning and expression analysis of the 2-on-2 Hb gene,GmGLB3, from soybean. TheGmGLB3 cDNA clone encodes a protein for 172 amino acid residues. Its deduced amino acid sequence shows the highest identity (74%) with 2-on-2 Hb fromMedicago truncatula. Multiple sequence alignment confirms the conserved and signature amino acid residues previously reported with plant 2-on-2 Hbs. Genomic Southern hybridization demonstrates thatGmGLB3 has two copies in the soybean genome. Based on our northern hybridization, theGmGLB3 gene is specifically expressed in root nodules, with levels increasing in the late stage during nodule development. Its transcript level is also increased under flooding and kinetin treatments in the roots, or under flooding and 2-iP treatments in the stems. However, no transcript is detected in the leaves regardless of treatment. Therefore, we propose that theGmGLB3 gene is specifically expressed in root nodules and that its expression in other plant organs is regulated by cytokinin and/or flooding.

Depigmentation and rejuvenation effects of kinetin on the aged skin of hairless descendants of Mexican hairless dogs.

The depigmenting and anti-aging effects of kinetin (KN) solutions on the aged skin of hairless dogs were clinically and histologically investigated. Grossly, all KN-treated sites became mildly depigmented. At 50 days of topical treatment with KN solutions, apparent improvement was observed in the skin texture, wrinkling, and pigmentation. At 100 days of KN treatment, both the skin rejuvenation and depigmentation effects became more prominent. Throughout the experimental period of KN treatment, no adverse effects were found in any sites treated with KN solutions. In the colorimetric system, at 100 days of topical treatment with KN solutions, the L* and b* values in the sites treated with KN solutions significantly increased. Histologically, at 50 days of topical treatment with KN solutions, the KN-treated sites showed a decrease in the thickness of the corneal layers. Melanin granules decreased throughout all epidermal layers. In the dermis, the large number of fine collagen and elastic fibers were densely aligned. At the end of the treatment, this agent was equally effective against pigmented lesions irrespective of the concentration of KN solution. The distribution of melanin granules returned to normal in the skin of adult hairless dogs. Throughout the present study, there were no histologic abnormalities in the epidermis and the dermis. These results revealed that topical treatment with lower concentrations of KN solutions normalized hyperpigmentation and improved the aged skin structure of hairless dogs. In addition, it was clarified that KN solutions had no adverse effects on the skin of hairless dogs and that this agent was a safe chemical for long-term application.

Correlation of cytokinin levels in the endosperms and roots with cell number and cell division activity during endosperm development in rice.

Cell number and cell division activity in rice (Oryza sativa) endosperms are possibly regulated by cytokinin levels in the endosperm and its source in the roots. This study tried to find the possible correlations among them. Six rice genotypes were grown in nutrient solution. Two patterns of endosperm cell division, synchronous and asynchronous, were observed among the genotypes based on the cell division rate of superior and inferior spikelets. Contents of zeatin (Z) + zeatin riboside (ZR) were much higher than those of N6-isopentenyladenine (iP) and N6-isopentenyladenosine (iPR) in both endosperms and roots. Changes in Z + ZR levels in endosperms were significantly correlated with those in roots, and both were very significantly correlated with the cell division rate. Changes in iP + iPR contents in the roots were not significantly correlated with those in the endosperms and the cell division rate. When roots were treated with kinetin, endosperm cell number and grain weight were increased. Such enhancement was more significantly achieved by the root kinetin treatment than by spraying kinetin on leaves and panicles. The results suggest that the cell number and cell division activity in rice endosperms are regulated by cytokinin levels in the endosperm and that root-derived Z + ZR play a pivotal role.

Kinetin, gibberellic acid and sucrose affect vase life in Oncidium spp

Cut Oncidium flowers were kept in open solutions. Kinetin at 50 mg.l−1 plus sucrose at 40 g.l−1 appeared to be more efficient in maintaining flower longevity than kinetin or sucrose alone. The flower longevity was longer with a kinetin pulse followed by a sucrose treatment than a continuous kinetin plus sucrose treatments. Gibberellic acid (GA3) had little effect on keeping flower longevity in Oncidium. Ethylene production was inhibited by the presence of sucrose. However, ethylene production was slightly stimulated by treatments of kinetin or GA3 alone as compared with HQS (8-hydroxyquinoline sulfate) controls. Similarly, ethylene production in kinetin plus sucrose, kinetin plus GA3 plus sucrose and GA3 plus sucrose was slightly enhanced compared with sucrose alone.

Nitrate reductase activity of radish cotyledons as affected by phytohormones and different nitrogen sources

Radish (Raphanus sativus L.) seedlings pretreated with different hormones viz. kinetin, gibberellic acid and abscisic acid were subjected to different N-forms. The seedlings were treated with different concentrations of KNO3, NH4Cl and NH4NO3 and the changes in nitrate reductase activity were seen in light and dark conditions in the cotyledons. Nitrate reductase activity was affected differently by hormone application. Nitrate increased and ammonia decreased nitrate reductase activity; in both light and dark-grown seedlings KNO3 induced more in vitro nitrate reductase activity. NH 4 + when combined with NO 3 − , however, could level up to some extent, with KNO3 in light, except in kinetin. A transient response of induction of NR activity was evident with decreased levels after a certain specific ambient N-concentration, despite the presence of high N in the medium. However, the pattern of transition varied with the hormones applied. Further, hormones are found to affect induction of different isoforms of nitrate reductase by NH 4 + and NO 3 − . NH 4 + induced isoform was prominently promoted by kinetin treatment in dark. The data documents a particular kind of interaction between controlling factors (light, N-source and phytohormones) which affect nitrate reductase levels.

Isolation of a gene from Arabidopsis thaliana related to nematode feeding structures.

Using a promoter tagging approach, a gene upregulated in nematode feeding structures (NFS) of Heterodera schachtii was identified in Arabidopsis thaliana plants. Sequence analysis of the transgenic line bearing gus reporter gene and the wild-type plant revealed that the T-DNA had been inserted into the promoter of the gene, however, with transcription start points at different sites for the gus reporter gene and for the endogenous gene. This tagged gene, designated pyk20, encodes a transcript of 2.6 kb. Southern blot analysis revealed a single gene copy for pyk20 in the Arabidopsis C-24 genome. Other cruciferous plants were shown to possess pyk20 or homologous genes. The predicted amino acid sequence of the PYK20 protein contains 695 residues with a molecular mass of 78 kDa and includes a glutamine-rich domain in the C-terminal region. IAA and kinetin treatment increased the level of the pyk20 transcript in the plant, whereas ABA treatment and temperature stress reduced the pyk20 transcript level. In-situ hybridisation and Northern blot analysis revealed that the gene is expressed in NFS. Based on homologies of the glutamine-rich domain, the biological role of the pyk20 gene product as a transcription factor is assumed.