Alternative oxidase involvement in Daucus carota somatic embryogenesis

Abstract

Plant alternative oxidase (AOX) is a mitochondrial inner membrane enzyme involved in alternative respiration. The critical importance of the enzyme during acclimation upon stress of plant cells is not fully understood and is still an issue of intensive research and discussion. Recently, a role of AOX was suggested for the ability of plant cells to change easily its fate upon stress. In order to get new insights about AOX involvement in cell reprogramming, quantitative real-time polymerase chain reaction (PCR) and inhibitor studies were performed during cell redifferentiation and developmental stages of Daucus carota L. somatic embryogenesis. Transcript level analysis shows that D. carota AOX genes (DcAOX1a and DcAOX2a) are differentially expressed during somatic embryogenesis. DcAOX1a shows lower expression levels, being mainly down-regulated, whereas DcAOX2a presented a large up-regulation during initiation of the realization phase of somatic embryogenesis. However, when globular embryos start to develop, both genes are down-regulated, being this state transient for DcAOX2a. In addition, parallel studies were performed using salicylhydroxamic acid (SHAM) in order to inhibit AOX activity during the realization phase of somatic embryogenesis. Embryogenic cells growing in the presence of the inhibitor were unable to develop embryogenic structures and its growth rate was diminished. This effect was reversible and concentration dependent. The results obtained contribute to the hypothesis that AOX activity supports metabolic reorganization as an essential part of cell reprogramming and, thus, enables restructuring and de novo cell differentiation.

Alternative oxidase (AOX) and phenolic metabolism in methyl jasmonate-treated hairy root cultures of Daucus carota L.

“…Similar enhancement in AOX transcript accumulation upon MJ treatment was previously reported in Capsicum annuum (Fung et al, 2004) and in Lycopersicon esculentum (Fung et al, 2006). In the present study, the DcAOX2a and DcAOX1a genes were chosen for correlation studies with phenylpropanoid biosynthesis because of known involvement of these two AOX genes in the process of developmental and cell reprogramming Frederico et al, 2009). Recently, Campos et al (2009) showed developmental and tissue specific differential transcript accumulation of DcAOX2a and DcAOX1a in D. carota.…”

“…SHAM (Aldrich, St. Louis, MO, USA) stock solution was prepared in dimethyl sulfoxide (Fluka BioChemika, St. Louis, MO, USA) essentially as described by Frederico et al (2009). From stock solution, different concentrations (0.1 mM, 0.2 mM, 0.4 mM, 0.5 mM and 0.8 mM) of SHAM were added to the liquid culture medium in conjugation with MJ (100 M).…”

“…The potential of AOX to affect redox and energy metabolism may serve to balance energy change and constant growth under a variety of changing environments (Moore et al, 2002). Inhibitors of both the phenylpropanoid pathway and AOX are known to suppress cell division and differentiation processes (Cvikrová et al, 2003;Frederico et al, 2009;Palama et al, 2010), which suggests a positive association between AOX and phenylpropanoid biosynthesis.…”

Genes and Trans-Factors Underlying Embryogenic Transition in Plant Soma-Cells

“…However, to sustain the cell-vigour up-regulation of mitochondrial alternative oxidase ( AOX ) gene was observed enhancing the defense mechanism of the cell mainly through lowering down the reactive oxygen production (Maxwell et al 1999 ). Similarly, in carrot two AOX genes ( Dc AOX1a and Dc AOX2a) have been examined up-regulated during initiation of SE (Frederico et al 2009 ).Thus the AOX gene family has been identifi ed having crucial role in plant SE. Ca 2+ is one of the most important signalling molecules participating in many cellular pathways and transmitting different signals.…”

Transgenic cassava lines carrying heterologous alternative oxidase (AtAOX1a) showed impaired quantitative and qualitative response to embryogenesis

“…The highest quality of the OES produced by the transgenic and the empty vector lines was 1.0. Somatic embryogenesis (SE), according to Frederico et al (2009), is the most prominent example of cell reprogramming, and has be interpreted as a stressinduced morphogenic response (Pasternak et al, 2002;Potters et al, 2007). The mitochondrion has been recognized to have strong effect on cell dedifferentiation (Amirsadeghi et al, 2007;Sheahan et al, 2005).…”