Defensinas de paantas y su uso potencial como controladores de plagas en la agricultrra / Plant Defensins and Their Potential Use as Pest Control in Agriculture

RESUMEN Las plantas, al igual que todos los organismos de la naturaleza, poseen elaborados sistemas de defensa contra patógenos, que pueden ser físicos y químicos, y producirse de forma constitutiva e inducida. Dentro de las barreras químicas inducidas se encuentra el grupo de proteínas de bajo peso molecular denominadas péptidos antimicrobianos (AMPs), al cual pertenecen las defensinas, péptidos con peso molecular entre 5 a 7 kDa, punto isoeléctrico de 9, y longitud de 45 a 55 aminoácidos; que tienen la capacidad de inhibir efectivamente el crecimiento de microorganismos fitopatógenos, en su mayoría hongos, y además, generan resistencia a condiciones abióticas de estrés en plantas. Este texto pretende realizar una descripción clara y actual de las características e investigaciones recientes con relación a las defensinas de plantas y sus más destacados usos en el control de patógenos en cultivos de importancia económica. Se plantea además la necesidad de profundizar en el conocimiento de dichas proteínas para su uso en estrategias de control tales como la producción de plantas y microorganismos transgénicos.

ABSTRACT Plants, as all organisms in nature, have elaborate systems of defense against pathogens; which can be physical or chemical and produced in a constitutive and induced way. Among the induced chemical barriers, there is a group of low molecular weight proteins, known as antimicrobial peptides (AMPs). These peptides include defensins, which are peptides with a molecular weight about 5 to 7 kDa, isoelectric point of 9, and length of about 45 to 55 amino acids. Likewise, they have the ability to avoid the growth of phytopathogenic microorganisms, mainly funguses. Moreover, these peptides create resistance to abiotic conditions of stress in plants. This manuscript seeks to make a clear and current description about the recent characteristics and researches related to plant defensins and their most significant uses in pathogens management in crops of economical relevance. It also intends to go deep into the study of such proteins in order to use them as a control strategy, such as production of transgenic plants and microorganisms.

Activity of Bacillus thuringiensis hybrid protein against a lepidopteran and a coleopteran pest.

The use of Cry proteins from Bacillus thuringiensis are an important strategy for biological control. Recently it has been demonstrated that Cry hybrid proteins (by domain swapping) resulted in improved toxicities in comparison with parental proteins. Here, an SN1917 hybrid toxin was constructed and tested against Colombian pest insects Tecia solanivora (Lepidoptera: Gelechiidae), a severe potato pest, and Hypothenemus hampei (Coleoptera: Scolytidae), which attacks coffee crops. The SN1917 protoxin had a concentration causing 50% mortality (LC(50)) of 392 ng cm(-2), and SN1917 toxin showed an LC(50) of 201 ng cm(-2) against T. solanivora first instar larvae. The two parental toxins (Cry1B and Cry1I) used to make this new hybrid protein caused a mortality of 60% and 52%, respectively. Unfortunately, H. hampei first instar larvae proved to be resistant to the toxin. We conclude that SN1917 is an option for biological control and resistance management of T. solanivora. Implications for H. hampei are discussed.