Mitochondrial bioenergetics and enzymatic antioxidant defense differ in Paraná pine cell lines with contrasting embryogenic potential

Abstract

Araucaria angustifolia is classified as a critically endangered species by the International Union for Conservation of Nature. This threat is worsened by the inefficiency of methods for ex-situ conservation and propagation. In conifers, somatic embryogenesis (SE) associated with cryopreservation is an efficient method to achieve germplasm conservation and mass clonal propagation. However, the efficiency of SE is highly dependent on genotype responsivity to the artificial stimulus used in vitro during cell line proliferation and later during somatic embryo development. In this study, we evaluated the activity of antioxidant enzymes and characterized mitochondrial functions during the proliferation of embryogenic cells of A. angustifolia responsive (SE1) and non-responsive (SE6) to the development of somatic embryos. The activities of the antioxidant enzymes GR (EC 1.6.4.2), MDHAR (EC 1.6.5.4), and POX (EC 1.11.1.7) were increased in SE1 culture, while in SE6 culture, only the activity of DHAR (EC 1.8.5.1) was significantly higher. Additionally, SE6 culture presented a higher number of mitochondria, which agreed with the increased rate of oxygen consumption compared to responsive SE1 culture; however, the mitochondrial volume was lower. Although the ATP levels did not differ, the NAD(P)H levels were higher in SE1 cells. NDs, AOX, and UCP were less active in responsive SE1 than in non-responsive cells. Our results show significant differences between SE1 and SE6 embryogenic cells regarding mitochondrial functions and antioxidant enzyme activities, which may be intrinsic to the in vitro proliferation phase of both cell lines, possessing a crucial role for the induction of in vitro maturation process.

Keywords:

• Mitochondria
• gymnosperm
• ROS
• bioenergetics
• embryogenesis

Acknowledgment

This investigation was supported by the Brazilian research funding agencies CNPq (ALDMF doctoral fellowship - process 140639/2014-4), CAPES (Finance code 001), and Fundação Araucária (Institutional Program for Basic and Applied Research - agreement 006/2017). The authors thank Paula Elbl for her assistance in the initial phase of this work.

Author contributions

ALDMF, FDK, and SMSCC planned and conducted all experiments and analyzed the data. GRM, LD, MEMR, ALWS, and EISF contributed to the design of experiments and interpretation of data. All authors participated in drafting and revising the manuscript. All authors approved the final version of the manuscript.

Disclosure statement

The authors declare that they have no conflicts of interest.