NaStEP, an essential protein for self-incompatibility in Nicotiana, performs a dual activity as a proteinase inhibitor and as a voltage-dependent channel blocker.

The S-specific pollen rejection response in Nicotiana depends on the interaction between S-RNase and a suite of SLF proteins. However, the biochemical pathway requires other essential proteins. One of them is the stigmatic protein NaStEP, which belongs to the Kunitz-type protease inhibitor family. Within the pollen tubes, NaStEP is a positive regulator of HT-B stability, likely inhibiting its degradation and, additionally, interacts with NaSIPP, a mitochondrial phosphate carrier. To gain a deeper understanding of the biochemical role of NaStEP in pollen rejection, we evaluated whether the activity of NaStEP as protease inhibitor is specific to a particular type of protease and whether it has the function of a voltage-dependent channel (VDC) blocker. Our findings indicate that, in vitro, NaStEP inhibits a subtilisin-like protease in an irreversible manner, but not other proteases, such as thermolysin and papain. Furthermore, we found that subtilisin processes the native NaStEP (24 kDa) into two lower molecular weight peptides of 21 and 14 kDa. Moreover, when we incubated NaStEP along with Xenopus leavis oocytes expressing the voltage-dependent potassium channel Kv 1.3, the current was blocked, indicating that NaStEP acts as a VDC blocker. These data allow us to propose NaStEP acts as a key molecule with two functions, one protecting HT-B from degradation by inhibiting a subtilisin-like protease and the second one by forming a complex with a mitochondrial VDC that could destabilize the mitochondria to trigger cell death, which would reinforce S-specific pollen rejection in Nicotiana.

Perfil antropométrico por posición de juego en handbolistas chilenos / Anthropometric profile in Chilean handball players according to playing position

El objetivo fundamental de la presente investigación fue determinar el perfil antropométrico y su relación con la capacidad de salto en jugadores de balonmano varones de la región de Valparaíso y de la Selección Chilena, esto en relación a su posición en el campo de juego. Se valoraron 74 jugadores de la categoría cadetes, cuyas edades fluctuaron entre los 14 y los 16 años, pertenecientes a los equipos: Club Italiano Villa Alemana, Club Italiano Quillota, Club Luterano, Club Viña del Mar, Club San José y Selección Chilena. Los resultados arrojaron que en cuanto a las variables antropométricas, la Selección Chilena y el Club Italiano Villa Alemana, son los que poseen los parámetros que más se asemejan a los requeridos a nivel competitivo dentro de esta categoría. Al hacer referencia a las variables antropométricas se estimó que, en todos los grupos estudiados, la masa adiposa se relacionó negativamente con la altura de salto alcanzada. Mientras que la masa muscular presentó una alta correlación con el rendimiento en salto en la mayoría de los equipos. Los índices de correlación evidenciaron que un menor porcentaje de masa grasa y mayor porcentaje de masa muscular favorecen la altura de salto alcanzada en todas las posiciones de juego. Queda de manifiesto que la relación masa adiposa y masa muscular es un indicador importante a la hora de determinar el rendimiento en la capacidad de salto en deportistas con características similares a las de este estudio.

The primary purpose of this research was to determine the relationship between the anthropometric profile and jump capacity of male handball players from the Fifth Region of Chile and the National Handball Team and their specific position in the playing field. In the evaluation 74 handball players participated from the following teams: Club Italiano Villa Alemana, Club Italiano Quillota, Club Luterano, Club Viña del Mar, Club San José and the National Handball Team. Participants were in the cadet category aged 14 ­ 16. The results showed that within anthropometric variables, players from the Chilean Handball Team and the Club Italiano Villa Alemana are the closest to fulfilling all the criteria required to reach high competitive levels in this category. In reference to anthropometric variables, fat mass proved to be negatively related to jump height reached in all groups tested, while muscle mass presented significant correlation with the jump capacity in most of the teams. Regarding the somatotype, results obtained agree with the theoretical referents. These establish that handball player's somatotype is more likely to be mesomorph. The correlation indexes demonstrate that a lower fat mass percentage and a higher muscle mass percentage enhance the jump capacity in all playing positions. It is clear now that fat mass and muscle mass are important indicators when determining the jump capacity performance in players with similar characteristics of the ones in this study. This research is important in setting comparative parameters in the selection process and sport specialization regarding anthropometric characteristics and jump capacity according to specific position of handball players in the cadet category.