Franciele Caixeta

Expression of genes related to tolerance to low temperature for maize seed germination

The aim of this study was to characterize maize lines tolerant to cold temperatures during the germination process. Seeds from lines with different levels of tolerance to low temperatures were used; 3 lines were classified as tolerant and 3 as susceptible to low germination temperatures. A field was set up to multiply seeds from selected lines. After the seeds were harvested and classified, we conducted physiological tests and analyzed fatty acid content of palmitic, stearic, oleic, linoleic, linolenic, and eicosenoic acids. In proteomic analysis, the expression of heat-resistant proteins, including catalase, peroxidase, esterase, superoxide dismutase, and α-amylase, were evaluated. Transcript analysis was used to measure the expression of the genes AOX1, AOX2, ZmMPK-17, and ZmAN-13. The material showing the highest susceptibility to low germination temperatures contained high saturated fatty acid content. Expression of α-amylase in seeds soaked for 72 h at a temperature of 10°C was lower than expression of α-amylase when soaked at 25°C for the same amount of time. We observed variation in the expression of heat-resistant proteins in seeds of the lines evaluated. The genes AOX and Zm-AN13 were promising for use in identifying maize materials that are tolerant to low germination temperatures.

Physiological and biochemical alterations during germination and storage of habanero pepper seeds

The objective of this study was to evaluate physiological and biochemical alterations during the development and storage of habanero pepper seeds with a view toward determining the time of harvest. Seeds were manually extracted from the fruit at three stages of development: E1 (fruit with first signs of yellowing), E2 (mature fruit) and E3 (mature fruit submitted to seven days of rest). After drying, seeds with 8% water content were stored at 10°C for 0, 4 and 8 months, and their quality evaluated by means of germination and vigor tests. Activities of the enzymes α-amylase, endo-β-mannanase, esterase, Superoxide Dismutase (SOD), malate dehydrogenase (MDH) and alcohol dehydrogenase (ADH) were evaluated during germination at 0, 48, 96 and 144 h after seeding. A randomized block design was used in a 3 × 3 factorial design (stages of development × storage) with 4 replications. Lower germination and vigor values were observed for the E1 stage seeds at all storage periods. In recently stored seeds, greater germination and vigor values were observed for the E3 stage seeds. Dormancy was observed principally in recently stored seeds and this was overcome at four months of storage. In summary, the physiological tests and activity of the enzymes evaluated indicated that the habanero pepper should be harvested at the E3 stage for a higher seed quality. Key words: Capsicum chinense, seed maturation, seed quality.

Aspectos fisiológicos e bioquímicos da germinação de sementes de alface em diferentes temperaturas

The objective of this work was to evaluate the electrophoretic patterns of heat-tolerant proteins and the activity of the endo-β-mannanase enzyme during lettuce seed germination, at high temperature. Seeds of eight lettuce cultivars were subjected to germination, first count, and emergence tests at two temperatures, 20 and 35oC. The index of germination speed (IVG) and the emergence rate index (IVE) were calculated. The expression of heat-tolerant proteins and of the endo-β-mannanase enzyme was also evaluated for all treatments. The experimental design was completely randomized, in a 2x8 factorial arrangement, with two temperatures and eight cultivars. The highest germination is observed at 35oC in the Everglades cultivar, considered thermotolerant. The patterns of heat-tolerant proteins in lettuce seeds present specific bands in the Everglades cultivar, at 35oC. The activity of the endo-β-mannanase enzyme is higher in the Everglades cultivar, at this temperature. This cultivar has potential for use in lettuce breeding programs aiming for tolerance to high temperatures during germination.

Determinação do ponto de colheita na produção de sementes de pimenta malagueta e alterações bioquímicas durante o armazenamento e a germinação

The harvest point interferes with the quality of the seeds, and in species with fleshy fruits and irregular maturation, there is difficulty in defining it. This study aimed to assess the dormancy of chili in three maturity stages during storage, in order to determine the best point of reaping and sowing and also enzymatic changes during the process of seed germination processed in different stages of maturation during storage. The seeds were manually extracted from fruits at three developmental stages: E1 (fruits with first signs of yellowing), E2 (ripe fruit) and E3 (mature and subjected to seven days of rest Fruits). After drying the seeds with 8% water content were stored in cold storage for 0, 4 and 8 months. After these periods seed quality was evaluated by means of the germination, vigor and enzyme activity tests. For the evaluation of the enzymes during the germination of seeds from each treatment, the seeds of each treatment were sampled for periods of 0, 48, 96 and 144 hours after sowing. We used a randomized block design, factorial trial 3 harvest times x 3 storage periods with Cientifica, Jaboticabal, v.42, n.2, p.187-197, 2014 ISSN: 1984-5529 188 four replications. There dormancy in seeds of chillies especially when newly stored and is surmounted by four months of storage. Chili seeds should be harvested when the E3 stage are sold after processing and at E2 or E3 when stored for periods up to four months. Enzyme changes are evident in the germination process and the different stages of maturation during storage. Additional keywords: Capsicum frutescens; seed maturation; seed quality.

Physiological quality of coffee seeds produced under different levels of solar radiation and maturation stages

In Brazil, although the coffee plantations are predominantly grown under full sunlight, the use of agroforestry systems can lead to socioeconomic advantages, thus providing a favorable environment to the crop by promoting its sustainability as well as environmental preservation. However, there is a lack of information on physiological quality of the coffee seeds produced under different levels of solar radiation. Within this context, the objective of this study was to evaluate the influence of different levels of solar radiation and maturation stages on the physiological quality of coffee (Coffea arabica L.) seeds, cv. Acaia Cerrado MG-1474. Three levels of solar radiation (plants grown under full sunlight; under plastic screens of 35% shading; and under plastic screens of 50% shading) and three maturation stages (cherry, greenish-yellow and green) were assessed. Physiological quality of seeds was assessed by using germination test, first count of germination, abnormal seedlings, dead seeds, and seedlings with open cotyledonary leaves. Electrophoretic analysis of isoenzymes catalase, esterase, superoxide dismutase and peroxidase was also performed. With the evolution of development the coffee seeds presents increases on physiological quality, and at its beginning the seeds show improvements on quality with the reduction of solar radiation.

Expression of genes associated with the biosynthetic pathways of abscisic acid, gibberellin, and ethylene during the germination of lettuce seeds

Seed germination and dormancy are complex phenomena that are controlled by many genes and environmental factors. Such genes are indicated by phytohormones that interact with each other, and may cause dormancy or promote seed germination. The objective of this study was to investigate gene expression associated with the biosynthetic pathways of abscisic acid (ABA), gibberellic acid (GA), and ethylene (ET) in dormant and germinated lettuce seeds. The expressions of LsNCED, LsGA3ox1, and ACO-B were evaluated in germinating and dormant seeds from the cultivars Everglades, Babá de Verão, Verônica, Salinas, Colorado, and Regina 71. The expressions of LsNCED, LsGA3ox1, and ACO-B were related to the biosynthesis of ABA, GA, and ET, respectively; therefore, the presence of these substances depends on genotype. LsNCED expression only occurred in dormant seeds, and was connected to dormancy. LsGA3ox1expression only occurred in germinated seeds, and was connected to germination. The ACO-B gene was involved in ET biosynthesis, and was expressed differently in germinated and dormant seeds, depending on the genotype, indicating different functions for different characteristics. Furthermore, sensitivity to phytohormones appeared to be more important than the expression levels of LsNCED, LsGA3ox1, or ACO-B.

Endo-β-mannanase and β-tubulin gene expression during the final phases of coffee seed maturation

Coffee seeds begin to develop shortly after fertilization and can take 6 to 8 months to complete their formation, a period during which all the characteristics of the mature seed are determined, directly influencing physiological quality. However, little is known about the molecular mechanisms that act during coffee seed maturation. The objective of the current study was to analyze expression of the β-tubulin (TUB) and endo-β-mannanase (MAN) genes during different phases at the end of development and in different tissues of Coffea arabica seeds. The transcription levels of the TUB and MAN genes were quantified in a relative manner using qRT-PCR in whole seeds, and dissected into embryos and endosperms at different developmental stages. Greater expression of MAN was observed in whole seeds and in endosperms during the green stage, and in the embryo during the over-ripe stage. High TUB gene expression was observed in whole seeds during the green stage and, in the embryos, there were peaks in expression during the over-ripe stage. In endosperms, the peak of expression occurred in both the green stage and in the cherry stage. These results suggest participation of endo-β-mannanase during the initial seed developmental stages, and in the stages of physiological maturity in the embryo tissues. TUB gene expression varied depending on the developmental stage and section of seed analyzed, indicating the participation of β-tubulin during organogenesis and coffee seed maturation.

Gene expression of antioxidant enzymes and coffee seed quality during pre- and post- physiological maturity

Seeds collected at different maturation stages vary in physiological quality and patterns of protective antioxidant systems against deterioration. In this study we investigated the expression of genes that codify catalase (CAT), dismutase superoxide (SOD), and polyphenol oxidase (PPO) during the pre- and post-physiological maturation phases in whole seeds and in endosperms and embryos extracted from the seeds. Coffea arabica L. berries were collected at the green, yellowish-green, cherry, over-ripe, and dry stages, and the seeds were examined physiologically. The transcription levels of the genes were quantified by quantitative real-time polymerase chain reaction using coffee-specific primers. The highest level of SOD expression was observed in the endosperm at the cherry and over-ripe stages; in addition, these seeds presented the greatest physiological quality (assessed via germination test). The highest CAT3 transcript expression was observed at the green stage in whole seeds, and at the green and over-ripe stages in the embryos and endosperms. High expression of the PPO transcript was observed at the green and yellowish-green stages in whole seeds. In embryos and endosperms, peak expression of the PPO transcript was observed at the green stage; subsequently, peaks at the cherry and over-ripe stages were observed. We concluded that the expression patterns of the SOD and CAT3 transcripts were similar at the more advanced maturation stages, which corresponded to enhanced physiological seed quality. High expression of the PPO transcript at the over-ripe stage, also observed in the embryos and endosperms at the cherry stage, coincided with the highest physiological seed quality.