Involvement of polyamines in the maturation of grapevine (Vitis vinifera L. ‘Mencía’) somatic embryos over a semipermeable membrane

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe endogenous content of polyamines and the expression of genes involved in their metabolism were analyzed in grapevine (Vitis vinifera L. ‘Mencía’) somatic embryo aggregates to determine the effect of a semipermeable membrane on their maturation in differentiation medium. The endogenous polyamine content in the somatic embryo aggregates was higher in those cultured over the semipermeable membrane and significantly increased with culture time due to an increase in the free polyamine fraction. Free putrescine represented more than 95% of the total free polyamine fraction and significantly peaked in the second week of culture of the somatic embryo aggregates over the semipermeable membrane. This finding appears to be supported by active expression of the VvADC gene and the low free spermidine level. Another significant peak of free putrescine was detected at the end of culture over the membrane, in which free spermidine level remained low despite the VvSPDS2 gene was upregulated. Hence, it is advisable that this increase in free putrescine was supported by back conversion from spermidine through VvPAO expression. As the semipermeable membrane successfully avoided precocious germination of the grapevine somatic embryos, the results support that polyamine metabolism, particularly putrescine metabolism, is involved in their correct maturation.Ministerio de Ciencia e Innovación | Ref. AGL2009–0748

Changes in abscisic acid metabolism in relation to the maturation of grapevine (Vitis vinifera L., cv. Mencía) somatic embryos

Background: Somatic embryogenesis in grapevines is a complex process that depends on many physiological and genetic factors. One of its main limitations is the process of precocious germination of the somatic embryos in differentiation medium. This process lowers plant conversion rates from the somatic embryos, and it is probably caused by a low endogenous abscisic acid (ABA) content.Results: Precocious germination of the somatic embryos was successfully avoided by culturing grapevine cv. Mencía embryogenic aggregates over a semipermeable membrane extended on top of the differentiation medium. The weekly analysis of the endogenous ABA and ABA-glucosyl ester (ABA-GE) contents in the aggregates showed their rapid accumulation. The expression profiles of 9-cis-epoxycarotenoid dioxygenase (VvNCED1), 8′-hydroxylase (VvHyd2), UDP-glucosyltransferase (VvUGT) and β-glucosidase (VvBG2) genes in grapevine revealed that the occurrence of a first accumulation peak of endogenous ABA in the second week of culture over the semipermeable membrane was mainly dependent on the expression of the VvNCED1 gene. A second increase in the endogenous ABA content was observed in the fourth week of culture. At this point in the culture, our results suggest that of those genes involved in ABA accumulation, one (VvNCED1) was repressed, while another (VvBG2) was activated. Similarly, of those genes related to a reduction in ABA levels, one (VvUGT) was repressed while another (VvHyd2) was activated. The relative expression level of the VvNCED1 gene in embryogenic aggregates cultured under the same conditions and treated with exogenous ABA revealed the significant downregulation of this gene.Conclusions: Our results demonstrated the involvement of ABA metabolism in the control of the maturation of grapevine somatic embryos cultured over a semipermeable membrane and two important control points for their endogenous ABA levels. Thus, subtle differences in the expression of the antagonistic genes that control ABA synthesis and degradation could be responsible for the final level of ABA during the maturation of grapevine somatic embryos in vitro. In addition, the treatment of somatic embryos with exogenous ABA suggested the feedback-based control of the expression of the VvNCED1 gene by ABA during the maturation of grapevine somatic embryos.Ministerio de Ciencia e Innovación | Ref. AGL2009-0748

Analysis of various inverters feeding induction motors with incipient rotor fault using high-resolution spectral analysis

Recently, there has been an increased interest in fault detection on electrical machines in steady-state regimes. Several frequency estimation techniques have been developed to assist the early detection of faults in induction motors, especially in line-fed motors. However, in modern industry, the use of inverters is increasingly present. This paper presents an analysis for comprehending the challenge in detecting incipient rotor faults using the stator current signal under different inverter supplies. The approach is based on the high-resolution technique known as multiple signal classification (MUSIC). In this study, incipient rotor faults in a squirrel-cage rotor, prior to the complete breaking of a rotor bar, are better identified in some inverters than others. The proposed approach finds the adequate MUSIC order that facilitates identification of bar breakage frequencies for early fault detection in each case studied from a wide set of trials. The study has been developed to detect incipient rotor bar breakages in an inverter-fed three-phase induction motor under varying load situations