RESUMEN
The voltage-dependent anion channel (VDAC) is the most abundant protein in the outer mitochondrial membrane (OMM) of all eukaryotes, having an important role in the communication between mitochondria and cytosol. The plant VDAC family consists of a wide variety of members that may participate in cell responses to several environmental stresses. However, there is no experimental information about the members comprising the maize VDAC (ZmVDAC) family. In this study, the ZmVDAC family was identified, and described, and its gene transcription profile was explored during the first six days of germination and under different biotic stress stimuli. Nine members were proposed as bona fide VDAC genes with a high potential to code functional VDAC proteins. Each member of the ZmVDAC family was characterized in silico, and nomenclature was proposed according to phylogenetic relationships. Transcript levels in coleoptiles showed a different pattern of expression for each ZmVDAC gene, suggesting specific roles for each one during seedling development. This expression profile changed under Fusarium verticillioides infection and salicylic acid, methyl jasmonate, and gibberellic acid treatments, suggesting no redundancy for the nine ZmVDAC genes and, thus, probably specific and diverse functions according to plant needs and environmental conditions. Nevertheless, ZmVDAC4b was significantly upregulated upon biotic stress signals, suggesting this gene's potential role during the biotic stress response.
RESUMEN
Moonlighting proteins are defined as proteins with two or more functions that are unrelated and independent to each other, so that inactivation of one of them should not affect the second one and vice versa. Intriguingly, all the glycolytic enzymes are described as moonlighting proteins in some organisms. Hexokinase (HXK) is a critical enzyme in the glycolytic pathway and displays a wide range of functions in different organisms such as fungi, parasites, mammals, and plants. This review discusses HXKs moonlighting functions in depth since they have a profound impact on the responses to nutritional, environmental, and disease challenges. HXKs' activities can be as diverse as performing metabolic activities, as a gene repressor complexing with other proteins, as protein kinase, as immune receptor and regulating processes like autophagy, programmed cell death or immune system responses. However, most of those functions are particular for some organisms while the most common moonlighting HXK function in several kingdoms is being a glucose sensor. In this review, we also analyze how different regulation mechanisms cause HXK to change its subcellular localization, oligomeric or conformational state, the response to substrate and product concentration, and its interactions with membrane, proteins, or RNA, all of which might impact the HXK moonlighting functions.
