Blanca E. Barrera-Figueroa

Isolation of dehydration-responsive genes in a drought tolerant common bean cultivar and expression of a group 3 late embryogenesis abundant mRNA in tolerant and susceptible bean cultivars

Drought is one of the main constraints for common bean (Phaseolus vulgaris L.) production in Latin America. The aim of this work was to identify upregulated genes in the drought-tolerant common bean cv. Pinto Villa, grown under water-deficit conditions. Twenty-eight cDNAs representing differentially-expressed mRNAs in roots and/or leaves were isolated via suppression subtractive hybridisation. Their expression profiles in plants under intermediate and severe dehydration stress were tested. Three cDNAs corresponded to genes already described as associated to drought stress in P. vulgaris, 12 were known P. vulgaris sequences without previous association with drought response, and 13 were new P. vulgaris sequences. Analysis of the deduced proteins encoded by the cDNAs revealed putative functions in cellular protection, sugar metabolism, and protein synthesis, folding and turnover. Additionally, a new member of group 3 late embryogenesis abundant (LEA) genes (PvLEA3) was cloned and its complete sequence was obtained. Given the lack of reports comparing expression of dehydration-responsive genes in bean cultivars with different response to drought, the expression of PvLEA3 transcript in five bean cultivars from different origin was analysed. The induction of PvLEA3 was directly associated with the level of drought tolerance in the cultivars studied.

Transcriptomic analysis of submergence-tolerant and sensitive Brachypodium distachyon ecotypes reveals oxidative stress as a major tolerance factor.

When excessive amounts of water accumulate around roots and aerial parts of plants, submergence stress occurs. To find the integrated mechanisms of tolerance, we used ecotypes of the monocot model plant Brachypodium distachyon to screen for genetic material with contrasting submergence tolerance. For this purpose, we used a set of previously studied drought sensitive/tolerant ecotypes and the knowledge that drought tolerance is positively associated with submergence stress. We decided to contrast aerial tissue transcriptomes of the ecotype Bd21 14-day-old plants as sensitive and ecotype Bd2-3 as tolerant after 2 days of stress under a long-day photoperiod. Gene ontology and the grouping of transcripts indicated that tolerant Bd2-3 differentially down-regulated NITRATE REDUCTASE and ALTERNATIVE OXIDASE under stress and constitutively up-regulated HAEMOGLOBIN, when compared with the sensitive ecotype, Bd21. These results suggested the removal of nitric oxide, a gaseous phytohormone and concomitant reactive oxygen species as a relevant tolerance determinant. Other mechanisms more active in tolerant Bd2-3 were the pathogen response, glyoxylate and tricarboxylic acid cycle integration, and acetate metabolism. This data set could be employed to design further studies on the basic science of plant tolerance to submergence stress and its biotechnological application in the development of submergence-tolerant crops.

Improvement of enzymatic saccharification yield in Arabidopsis thaliana by ectopic expression of the rice SUB1A-1 transcription factor

Saccharification of polysaccharides releases monosaccharides that can be used by ethanol-producing microorganisms in biofuel production. To improve plant biomass as a raw material for saccharification, factors controlling the accumulation and structure of carbohydrates must be identified. Rice SUB1A-1 is a transcription factor that represses the turnover of starch and postpones energy-consuming growth processes under submergence stress. Arabidopsis was employed to test if heterologous expression of SUB1A-1 or SUB1C-1 (a related gene) can be used to improve saccharification. Cellulolytic and amylolytic enzymatic treatments confirmed that SUB1A-1 transgenics had better saccharification yield than wild-type (Col-0), mainly from accumulated starch. This improved saccharification yield was developmentally controlled; when compared to Col-0, young transgenic vegetative plants yielded 200–300% more glucose, adult vegetative plants yielded 40–90% more glucose and plants in reproductive stage had no difference in yield. We measured photosynthetic parameters, starch granule microstructure, and transcript abundance of genes involved in starch degradation (SEX4, GWD1), juvenile transition (SPL3-5) and meristematic identity (FUL, SOC1) but found no differences to Col-0, indicating that starch accumulation may be controlled by down-regulation of CONSTANS and FLOWERING LOCUS T by SUB1A-1 as previously reported. SUB1A-1 transgenics also offered less resistance to deformation than wild-type concomitant to up-regulation of AtEXP2 expansin and BGL2 glucan-1,3,-beta-glucosidase. We conclude that heterologous SUB1A-1 expression can improve saccharification yield and softness, two traits needed in bioethanol production.

Biotechnological Strategies to Improve Plant Biomass Quality for Bioethanol Production

The transition from an economy dependent on nonrenewable energy sources to one with higher diversity of renewables will not be a simple process. It requires an important research effort to adapt to the dynamics of the changing energy market, sort costly processes, and avoid overlapping with social interest markets such as food and livestock production. In this review, we analyze the desirable traits of raw plant materials for the bioethanol industry and the molecular biotechnology strategies employed to improve them, in either plants already under use (as maize) or proposed species (large grass families). The fundamentals of these applications can be found in the mechanisms by which plants have evolved different pathways to manage carbon resources for reproduction or survival in unexpected conditions. Here, we review the means by which this information can be used to manipulate these mechanisms for commercial uses, including saccharification improvement of starch and cellulose, decrease in cell wall recalcitrance through lignin modification, and increase in plant biomass.

Los métodos experimentales que permiten el estudio de las macromoléculas de la vida: historia, fundamentos y perspectivas

Experimental methods that allow the study of the macromolecules of life: history, fundamentals and perspectives Nucleic acids and proteins comprise a network of biomacromolecules that store and transmit information sustaining the life of the cell. The study of these mechanisms is a field called molecular biology. The development of this science has always been paired with technical advances that allow breaking through methodological barriers in order to test novel hypothesis. Among available methods for molecular biologists, five stand: electrophoresis, sequencing, cloning, blotting and polymerase chain reaction. Their impact reaches genetics, medicine and biotechnology. Here, the historic relevance, technical grounds and current trends of these five essential methods are reviewed. The review intends to be useful both for students and professional scientists who seek to acquire advanced knowledge on the value of these methods to probe the molecular mechanisms sustaining life.

Oryza granulata Nees et Arn. ex Watt

Oryza granulata Nees et Arn. ex Watt is a wild rice species with importance as a resource for the study of genetic diversity and evolution of the Oryza genus, and for the identification of genes and regulatory networks with a potential use in the improvement of tolerance to biotic and abiotic stress in cultivated rice. In this chapter, we reviewed the biology, distribution, genetic diversity, genome resources, and advances on the study of O. granulata genome.

Demostraciones prácticas de los retos y oportunidades de la producción de bioetanol de primera y segunda generación a partir de cultivos tropicales

Practical demonstrations of challenges and opportunities on first and second generation bioethanol production using tropical crops) Modern society depends on non-renewable energy sources like petroleum hydrocarbons for trans- portation fuel. There is currently a great interest in developing new sources and processes for biofu- els. Ethanol is a promising biofuel obtained from carbohydrate fermentation by bakers yeast ( Sac- charomyces cerevisiae). In this work, we present a set of teaching lab sessions where students prepare fermentations and produce first (free sugars and starch) and second (cellulose) generation bioetha - nol. Several carbohydrate sources produced in the tropical regions of Mexico and the Americas were tested, for example, juice (pineapple, sugarcane, grape and apple), tuberous crops (cassava, potato and sweet potato) and cellulose (sugarcane leaves and recycled paper). Sessions were developed as supervised research projects and students learnt and discussed the principles and challenges of etha- nol biofuel production.