Heterosis in the freezing tolerance of crosses between two Arabidopsis thaliana accessions (Columbia‐0 and C24) that show differences in non‐acclimated and acclimated freezing tolerance

Abstract

SummaryHeterosis is broadly de®ned as the increased vigour of hybrids in comparison to their parents. In the model plant Arabidopsis thaliana, a signi®cant heterosis effect on leaf-freezing tolerance was observed in the F 1 generation of a cross between the accessions Columbia-0 (Col) and C24. Parental Col plants were signi®-cantly more freezing-tolerant than C24 plants in both the acclimated and non-acclimated (NA) states. Midparent heterosis was observed in the F 1 plants, both in the basic tolerance of non-adapted plants and in freezing tolerance after cold acclimation. Best-parent heterosis, on the other hand, was only found after cold acclimation. The heterosis effect was reduced in the F 2 populations such that only mid-parent heterosis was evident. The leaf content of soluble sugars (fructose (Fru), glucose (Glc), sucrose (Suc) and raf®nose (Raf)) increased dramatically in the F 1 plants after cold acclimation as compared to the parental lines. The content of proline (Pro), however, was only moderately increased in the F 1 plants under the same conditions. Correlation analyses showed that only Raf content was consistently related to leaf-freezing tolerance in both the acclimated and NA states. A quanti®cation of mRNA levels in leaves of parental and F 1 lines using quantitative real-time RT-PCR showed no clear indication for an involvement of the investigated genes (CBF (C-repeat binding factor)1, CBF2, (cold-regulated protein (COR ) 6.6, COR15a, COR15b, COR47 and COR78 ) in the heterosis effect.

Disordered Cold Regulated15 Proteins Protect Chloroplast Membranes during Freezing through Binding and Folding, But Do Not Stabilize Chloroplast Enzymes in Vivo

“…As shown in Figure 2, freezing tolerance is expressed as the temperature at which 50% damage occurred or LT 50 . In wild-type plants, the LT 50 of cold-acclimated leaves was about 4°C lower than that of nonacclimated leaves, in agreement with previously published values for the accession Columbia-0 of Arabidopsis (Col-0; Rohde et al, 2004;Zuther et al, 2012). Under nonacclimated conditions, no significant effect of COR15 silencing on leaf freezing tolerance was observed.…”

“…The effect of altered COR15 protein levels on Arabidopsis freezing tolerance was tested using two independent approaches: an electrolyte leakage assay to assess freezing damage to the plasma membrane and the tonoplast (Rohde et al, 2004), and a chlorophyll fluorescence imaging assay to obtain information on the inactivation of photosynthesis and the intactness of chloroplast membranes (Ehlert and Hincha, 2008). As shown in Figure 2, freezing tolerance is expressed as the temperature at which 50% damage occurred or LT 50 .…”

“…Plants were grown in soil in a greenhouse at 16-h day length with light supplementation to reach at least 200 mE m 22 s 21 and temperatures of 20°C during the day and 18°C during the night until 42 d after sowing (nonacclimated plants). For cold acclimation, plants were transferred to a 4°C growth cabinet (16-h day/8-h night cycle, 4°C) with 90 mE m 22 s 21 for an additional 14 d (Rohde et al, 2004). Phosphotricine resistance was used as a selectable marker to identify homozygous transgenic plant lines.…”

Cold tolerance in cypress (Cupressus sempervirens L.): a physiological and molecular study

“…Several methods have been developed to quantify the frost damage to plant membranes. The most frequently used is the determination of electrolyte leakage from plant tissue after freezing and thawing using conductivity measurements (Rohde et al 2004). This method provides information about the ability of plant membranes to function as a semi-permeable barrier for intracellular ions, but does not take into account the damage to chloroplast membranes.…”

Self-Incompatibility in the Brassicaceae

“…Reverse genetic tools for many commonly used Arabidopsis accessions are still limited, in particular accession C24, which is genetically distinct from accession Col-0 (Barth et al 2002 ;Törjek et al 2003 ). C24 is distinguished physiologically from other familial accessions in terms of tolerance to drought (Bechtold et al 2010 ), ozone (Brosche et al 2010 ), and frost (Rohde et al 2004 ), and enhanced basal resistance to pathogens (Bechtold et al 2010 ). The transgenic A. thaliana accession C24 also exhibited a robust and stable self-incompatible (SI) phenotype (Rea et al 2010 ), which served as a good model for understanding SI signaling.…”