Piyada Theerakulpisut

Exogenous proline and trehalose promote recovery of rice seedlings from salt-stress and differentially modulate antioxidant enzymes and expression of related genes.

Proline (Pro) and Trehalose (Tre) function as compatible solutes and are upregulated in plants under abiotic stress. They play an osmoprotective role in physiological responses, enabling the plants to better tolerate the adverse effects of abiotic stress. We investigated the effect of exogenous Pro and Tre (10 mM) in seedlings of Thai aromatic rice (cv. KDML105; salt-sensitive) during salt stress and subsequent recovery. Salt stress (S, NaCl) resulted in growth reduction, increase in the Na(+)/K(+) ratio, increase in Pro level and up-regulation of Pro synthesis genes (pyrroline-5-carboxylatesynthetase, P5CS; pyrroline-5-carboxylate reductase, P5CR) as well as accumulation of hydrogen peroxide (H(2)O(2)), increased activity of antioxidative enzymes (superoxide dismutase, SOD; peroxidase, POX; ascorbate peroxidase, APX; catalase, CAT) and transcript up-regulation of genes encoding antioxidant enzymes (Cu/ZnSOD, MnSOD, CytAPX, CatC). Under salt stress, exogenous Pro (PS; Pro+NaCl) reduced the Na(+)/K(+) ratio, further increased endogenous Pro and transcript levels of P5CS and P5CR, but decreased the activity of the four antioxidant enzymes. The transcription of genes encoding several antioxidant enzymes was upregulated. Exogenous Tre (TS; Tre+NaCl) also reduced the Na(+)/K(+) ratio and strongly decreased endogenous Pro. Transcription of P5CS and P5CR was upregulated, the activities of SOD and POX decreased, the activity of APX increased and the transcription of all antioxidant enzyme genes upregulated. Although exogenous osmoprotectants did not alleviate growth inhibition during salt stress, they exhibited a pronounced beneficial effect during recovery period showing higher percentage of growth recovery in PS (162.38%) and TS (98.43%) compared with S (3.68%). During recovery, plants treated with PS showed a much greater reduction in endogenous Pro than NaCl-treated (S) or Tre-treated plants (TS). Increase in CAT activity was most related to significant reduction in H(2)O(2), particularly in the case of PS-treated plants. Advantageous effects of Pro were also associated with increase in APX activity during recovery.

Cloning sequencing of Lol pI, the major allergenic protein of rye-grass pollen

We have isolated a full length cDNA clone encoding the major glycoprotein allergen Lol pI. The clone was selected using a combination of immunological screening of a cDNA expression library and PCR amplification of Lol pI‐specific transcripts. Lol pI expressed in bacteria as a fusion protein shows recognition by specific IgE antibodies present in sera of grass pollen‐allergic subjects. Northern analysis has shown that the Lol pI transcripts are expressed only in pollen of rye‐grass. Molecular cloning of Lol pI provides a molecular genetic approach to study the structure—function relationship of allergens.

Isolation and developmental expression of Bcp1, an anther-specific cDNA clone in Brassica campestris.

Differential screening of a mature Brassica campestris pollen cDNA library has identified five cDNA clones that represent transcripts expressed exclusively, or at elevated levels, in pollen. We show here that the expression of one of these, clone Bcp1, is tissue specific and temporally regulated. The gene is activated during microspore development, as detected by in situ hybridization. Expression is enhanced at the time of pollen maturation and during pollen germination. In situ hybridization has also shown that Bcp 1 is activated in the tapetal cells in early anther development and continues to be expressed until tapetal dissolution. Homologous transcripts are present in pollen of other taxa of Brassicaceae including Arabidopsis, but not in pollen of any other families tested.

Cloning, expression and immunological characterization of Ory s 1, the major allergen of rice pollen.

We have isolated and characterized a cDNA clone, Ory s 1, encoding a group-1 allergen of rice pollen. The Ory s 1 protein shows significant sequence identity to the major allergen of rye-grass pollen, Lol p 1. RNA gel blot analysis shows that the Ory s 1 gene is expressed in mature anthers, but not in vegetative or other floral tissues tested. Southern blot analysis indicates that this clone represents a member of a small gene family in rice. Western blot analyses of total rice pollen proteins with the group-1 allergen-specific monoclonal 3A2 and IgE antibodies from grass pollen-allergic patients, revealed the presence of cross-reactive antigenic and allergenic epitopes in Ory s 1.

Physiological and biochemical parameters for evaluation and clustering of rice cultivars differing in salt tolerance at seedling stage

Salinity tolerance levels and physiological changes were evaluated for twelve rice cultivars, including four white rice and eight black glutinous rice cultivars, during their seedling stage in response to salinity stress at 100 mM NaCl. All the rice cultivars evaluated showed an apparent decrease in growth characteristics and chlorophyll accumulation under salinity stress. By contrast an increase in proline, hydrogen peroxide, peroxidase (POX) activity and anthocyanins were observed for all cultivars. The K+/Na+ ratios evaluated for all rice cultivars were noted to be highly correlated with the salinity scores thus indicating that the K+/Na+ ratio serves as a reliable indicator of salt stress tolerance in rice. Principal component analysis (PCA) based on physiological salt tolerance indexes could clearly distinguish rice cultivars into 4 salt tolerance clusters. Noteworthy, in comparison to the salt-sensitive ones, rice cultivars that possessed higher degrees of salt tolerance displayed more enhanced activity of catalase (CAT), a smaller increase in anthocyanin, hydrogen peroxide and proline content but a smaller drop in the K+/Na+ ratio and chlorophyll accumulation.

Effect of shading on yield, sugar content, phenolic acids and antioxidant property of coffee beans (Coffea Arabica L. cv. Catimor) harvested from north-eastern Thailand.

BACKGROUND Environmental conditions, including shading, generally influence the physical and chemical qualities of coffee beans. The present study assessed the changes in some phenolic compounds, antioxidant activity and agronomic characters of coffee beans (Coffea arabica L. cv. Catimor) as affected by different shading conditions including full sun, three artificial shading conditions using a saran covering (50% shade, 60% shade, and 70% shade) and lychee shade. RESULTS Bean weight and bean size increased significantly (P < 0.05) when the shade level was progressively increased. The coffee beans grown under lychee shade exhibited superior bean yield, 1000-bean weight, total phenolic content and antioxidant activity compared to all other beans. Chlorogenic acid was the most predominant phenolic acid in all samples studied, being the highest in the beans grown under lychee shade, followed by 60% shade, 70% shade, 50% shade and full sun, respectively. In contrast, bean grown under full sun had the highest amount of vanillic acid and caffeic acid. CONCLUSIONS Antioxidant activity was highly positively associated with chlorogenic acid content. The content of total sugar (fructose, glucose and sucrose) was found highest in coffee beans grown in 60% shade, with fructose the predominant sugar. Under climatic conditions similar to this experiment, it is advisable that growers provide shade to the coffee crop to reduce heat from direct sunlight and promote yield as well as obtain good quality coffee beans.

Environmentally benign synthesis of phytochemicals-capped gold nanoparticles as nanopriming agent for promoting maize seed germination

Application of nanotechnology in agriculture is moving towards to improve the cultivation and growth of crop plants. The present study is the first attempt to propose a simple, yet cost-effective and ecofriendly synthesis of phytochemicals-capped GNPs using rhizome extract of galanga plant at room temperature. The synthesized GNPs were characterized by various characterization techniques. To promote the green nanotechnology applications in agriculture, GNPs solution at environmentally realistic dose (5 to 15ppm) as nanopriming agent was used to activate the germination and early seedling growth of maize aged seeds. Priming with 5ppm GNPs showed the best effects on promoting emergence percentage (83%) compared to unprimed control (43%) and hydroprimed groups (56%). Seed priming at both 5 and 10ppm GNPs also enhanced seedling vigor index by 3 times over the control. Priming with GNPs at 10ppm was found to enhance the best physiological and biochemical properties of maize seedlings. Internalization studies by inductively coupled plasma atomic emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM) strongly supported that GNPs can internalize into seeds. However, ICP-OES analysis revealed that GNPs were not present in both shoot and root parts, suggesting that nanopriming approach minimizes the Au translocation from seeds into plant vegetative organs. Phytosynthesized GNPs were found to be less toxic than chemically synthesized GNPs. This is the first report showing phytochemicals-capped GNPs as a promising nanopriming agent for activating the germination of naturally aged seeds of crop plant.

Effects of Salt Stress after Late Booting Stage on Yield and Antioxidant Capacity in Pigmented Rice Grains and Alleviation of the Salt-Induced Yield Reduction by Exogenous Spermidine

Abstract Pigmented rice is receiving much attention due to the large amounts of bioactive compounds and various health benefits.However, little information is available on its agronomic and physiological aspects. This research aimed to explore the effects of salinity on yield and grain quality of pigmented rice and the modulation of salinity responses by exogenous application of spermidine (Spd). Four cultivars of rice were grown in pots until the early booting stage. Thereafter, the plants were sprayed with 1 mM Spd for 7 successive days before being irrigated with 25 mM NaCl instead of tap water until maturity. Grain yield, yield components and harvest index in all rice cultivars were negatively affected by this salinity stress. Pretreatment with Spd dramatically improved yield and yield components of salt-treated plants, particularly the salt-sensitive cultivar. The major yield components which were improved and contributed most to the dramatic increase in seed yield were the number of filled grains per panicle and panicle fertility. Moreover, Spd pretreatment resulted in an increase in K+/Na+ ratio in rice grains. Salt stress increased nutritional quality of mature grains, i.e., total phenolic content, anthocyanins, proanthocyanins and antioxidant activities (evaluated by FRAP, DPPH and ABTS assays) in all rice cultivars. Furthermore, all aspects of health-promoting nutritional characters were further enhanced by Spd pretreatment. Thus foliar spraying of Spd to rice plants prior to salt application improved grain yield as well as nutritional quality of colored rice grains in relation to total phenolics, flavonoid pigments and antioxidant capacities.

Isolation of a gene preferentially expressed in mature anthers of rice (Oryza sativa L.)

SummaryUsing monoclonal antibodies raised against pollen-specific proteins, we have isolated a cDNA clone, designatedOry-Cl from a rice anther cDNA expression library. A transcript corresponding to theOry-Cl gene showed preferential expression in anthers. This transcript was not detected in any vegetative tissues analysed. RNA gel blot analysis of different developmental stages of anthers showed that theOry-Cl gene is expressed at later stages of pollen development. In situ hybridisation showed that theOry-Cl transcript is only present in mature pollen.

Salt-responsive mechanisms in chromosome segment substitution lines of rice (Oryza sativa L. cv. KDML105)

Two chromosome segment substitution lines of Khao Dawk Mali 105 (KDML105) rice that carry quantitative trait loci for drought tolerance located on chromosome 8 (DT-QTL8) designated CSSL8-94 and CSSL8-116 were investigated for co-expression network and physiological responses to salinity compared to their parents (KDML105; drought and salt sensitive recurrent parent, and DH103; drought tolerant QTL donor). These CSSL lines show different salt-response traits under salt stress (CSSL8-94 shows higher tolerance than CSSL8-116) and possess different segments of DT-QTL8. To identify specific biological process(es) associated with salt-stress response, co-expression network analysis was constructed from each DT-QTL segment. To evaluate differential physiological mechanisms responding to salt stress, all rice lines/cultivar were grown for 21 d in soils submerged in nutrient solutions, then subjected to 150 mM NaCl for 7 d. Physiological parameters related to co-expression network analysis (photosynthetic parameters) and salt responsive parameters (Na(+)/K(+) ratio, proline content, malondialdehyde and ascorbate peroxidase activity; EC1.11.1.1) were investigated along with the expression analysis of related genes. Physiological responses under salt stress particularly photosynthesis-related parameters of CSSL8-94 were similar to DH103, whereas those of CSSL8-116 were similar to KDML105. Moreover, expression levels of photosynthesis-related genes selected from the co-expression networks (Os08g41460, Os08g44680, Os06g01850, Os03g07300 and Os02g42570) were slightly decreased or stable in CSSL8-94 and DH103 but were dramatically down-regulated in CSSL8-116 and KDML105. These differential responses may contribute to the photosynthesis systems of CSSL8-94 being less damaged under salt stress in comparison to those of CSSL8-116. It can be concluded that the presence of the specific DT-QTL8 segment in CSSL8-94 not only confers drought tolerant traits but also enhances its salt tolerant ability.