One of the strategies to overcome diseases or abiotic stress in crops is the use of improved varieties. Genetic improvement could be accomplished through different methods, including conventional breeding, induced mutation, genetic transformation, or gene editing. The gene function and regulated expression through promoters are necessary for transgenic crops to improve specific traits. The variety of promoter sequences has increased in the generation of genetically modified crops because they could lead to the expression of the gene responsible for the improved trait in a specific manner. Therefore, the characterization of the promoter activity is necessary for the generation of biotechnological crops. That is why several analyses have focused on identifying and isolating promoters using techniques such as reverse transcriptase-polymerase chain reaction (RT-PCR), genetic libraries, cloning, and sequencing. Promoter analysis involves the plant genetic transformation method, a potent tool for determining the promoter activity and function of genes in plants, contributing to understanding gene regulation and plant development. Furthermore, the study of promoters that play a fundamental role in gene regulation is highly relevant. The study of regulation and development in transgenic organisms has made it possible to understand the benefits of directing gene expression in a temporal, spatial, and even controlled manner, confirming the great diversity of promoters discovered and developed. Therefore, promoters are a crucial tool in biotechnological processes to ensure the correct expression of a gene. This review highlights various types of promoters and their functionality in the generation of genetically modified crops.

Bananas and plantains are considered an important crop around the world. Banana production is affected by several constraints, of which Black Sigatoka Disease, caused by the fungus Mycosphaerella fijiensis, is considered one of the most important diseases in banana plantations. The banana accession ‘Calcutta-4’ has a natural resistance to Black Sigatoka; however, the fruit is not valuable for commercialization. Gene identification and expression studies in ‘Calcutta-4’ might reveal possible gene candidates for resistant to the disease and elucidate mechanisms for resistance. A subtracted cDNA library was generated from leaves after 6, 9 and 12 days inoculated with M. fijiensis conidia on greenhouse banana plants of the accession ‘Calcutta-4’. Bioinformatic analysis revealed 99 good quality sequences. Blast2go analysis revealed that 31% of the sequences could not be categorized and, according to the Biological Process Category, 32 and 28 ESTs are related to general metabolic and cellular processes, respectively; while 10 ESTs response to stimulus. Seven sequences were redundant and one was similar to genes that may be involved in pathogen resistance including the putative disease resistance protein RGA1. Genes encoding zinc finger domains were identified and may play an important role in pathogen resistance by inducing the expression of downstream genes. Expression analysis of four selected genes was performed using RT-qPCR during the early stage of the disease development at 6, 9, 12 and 15 days post inoculation showing a peak of up regulation at 9 or 12 days post inoculation. Three of the four genes showed an up-regulation of expression in ‘Calcutta-4’ when compared to ‘Williams’ after inoculation with M. fijiensis, suggesting a fine regulation of specific gene candidates that may lead to a resistance response. The genes identified in early responses in a plant-pathogen interaction may be relevant for the resistance response of ‘Calcutta-4’ to Black Sigatoka. Genes with different functions may play a role in plant response to the disease. The present study suggests a fine up regulation of these genes that might be needed to perform an incompatible interaction. Further gene functional studies need to be performed to validate their use as candidate resistance genes in susceptible banana cultivars.

ISHS XXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposium on Molecular Biology in Horticulture Status and challenges of genetically modified crops and food in Ecuador

The use of environmental-friendly agricultural inputs to increase yield in crops could reduce environmental contamination and alleviate (a)biotic stress. In this study, we applied a foliar liquid biostimulant to banana plants, which was developed from the anaerobic fermentation of microorganisms with organic remains (manure and plant waste) and minerals to use as environmental-friendly product. To determine the effect of this biostimulant in the plants, a Suppression Subtractive Hybridization (SSH) library was developed from banana leaves in greenhouse conditions. Furthermore, salicylic and jasmonic pathways activation was evaluated by gene expression analysis. First, the application of the biostimulant to banana leaves increased the membrane stability index (MSI), which is directly related to a higher CO₂ exchange and assimilation rate. Additionally, the total chlorophyll content increased in plants in comparison with the control plants. In addition, the SSH analysis revealed around 300 expressed sequence tags (ESTs). Several induced genes associated with different molecular pathways, including photosynthesis, anthocyanins production, and plant defense, among others, were encountered after bioinformatic analysis. Upregulated gene expression was demonstrated in different time points, after biostimulant application. Furthermore, induced expression of genes related to the jasmonic acid pathway was observed, which may prove beneficial to the plant under stress conditions.

Two subtractive cDNA libraries from banana leaves (cultivar 'Williams', genotype AAA) after biostimulant application on the leaf (library 1) or the substrate (library 2), with Pseudocercospora fijiensis infection were generated. The banana plants were applied first with the biostimulant and later the inoculation of P. fijiensis was performed on the leaves after one week. The suppression subtractive hybridization was performed by using as tester the treatments with biostimulant application by sampling banana leaves after two weeks of P. fijiensis inoculation, and every two weeks for two months (four time points); while the driver were collected on the same dates on independent banana plants that were only inoculated with P. fijiensis (no biostimulant application). The plants were maintained in the greenhouse for the entire assay.