ABSTRACT
Hpa1 is a harpin protein produced by Xanthomonas oryzae, an important bacterial pathogen of rice, and has the growth-promoting activity in plants. To understand the molecular basis for the function of Hpa1, we generated an inactive variant protein, Hpa1ΔNT, by deleting the nitroxyl-terminal region of the Hpa1 sequence and compared Hpa1ΔNT with the full-length protein in terms of the effects on vegetative growth and related physiological responses in Arabidopsis. When Hpa1 was applied to plants, it acted to enhance the vegetative growth but did not affect the floral development. Enhanced plant growth was accompanied by induced expression of growth-promoting genes in plant leaves. The growth-promoting activity of Hpa1 was further correlated with a physiological consequence shown as promoted leaf photosynthesis as a result of facilitated CO2 conduction through leaf stomata and mesophyll cells. On the contrary, plant growth, growth-promoting gene expression, and the physiological consequence changed little in response to the Hpa1ΔNT treatment. These analyses suggest that Hpa1 requires the nitroxyl-terminus to facilitate CO2 transport inside leaf cells and promote leaf photosynthesis and vegetative growth of the plant.
ABSTRACT
La hemoglobina es una proteína sanguínea que puede transportar oxígeno, un gas insoluble en medio acuoso, llevándolo a las diferentes partes del organismo en donde es requerido para su buen funcionamiento, así como productos metabólicos como el CO2 y el hidrógeno, para su excreción. Estos procesos se ven condicionados por factores como el pH, la concentración de BPG, las presiones parciales de O2 y CO2, la cooperatividad de la unión entre la hemoglobina y esos compuestos y los cambios conformacionales que la hemoglobina debe sufrir para captar y soltar eficientemente estas moléculas en el sitio del organismo donde son requeridos. Cambios abruptos en la presión atmosférica ligados a la altura, y la exposición a altas concentraciones de otros gases afines a la hemoglobina como el monóxido de carbono, presente en vehículos o recintos cerrados, pueden comprometer el funcionamiento normal del organismo precisamente porque causan efectos sobre esa función transportadora de la hemoglobina. En este escrito, se explicarán fenómenos de la vida diaria relacionados con el transporte de gases por la hemoglobina, como una demostración de que los conocimientos bioquímicos comienzan a ser útiles desde ahora para entender situaciones cotidianas y a dejarnos la expectativa de su valor para entender muchos de los problemas de salud que tendremos en nuestras manos.
The hemoglobin is a blood protein which can transport oxygen, a gas insoluble in water, to different organs where it is required for the proper function; this protein also transports the metabolic products, CO2 and H+ for their excretion. This process depends on pH, the BPG concentration, pO2 and pCO2. The cooperative binding between hemoglobin and those compounds and the conformational changes necessary for oxygen and CO2 uptake and release in the specific place where they are required. Abrupt changes of atmospheric pressure associated with height and the exposure to other gases such as CO present in vehicles and closed rooms could compromise the normal functioning of the organism because their presence affects the transport function of the hemoglobin. In this paper, we will explain everyday phenomena related to the transport of gases through hemoglobin as a demonstration that a knowledge of biochemistry begins to be useful from now on to understand everyday situations and give us an expectation of their value to comprehend many health problems that would be faced in the future.