Engineering carpel-specific cold stress tolerance: a case study in Arabidopsis

Oxidative stress level and dehydrin gene expression pattern differentiate two contrasting cucumber F1 hybrids under high fertigation treatment

Two cucumber F1 cultivar hybrids were investigated for stress tolerance markers upon application of different strength of Hoagland fertigation solutions (HG). 'Joker' and 'Oitol' cultivar hybrids were studied, representing typically field grown and greenhouse cultivated genotypes, respectively. At standard fertigation level (0.5 × HG) in controlled environment young 'Joker' plants displayed slower growth than 'Oitol' based on total leaf area. At this basal nutrient concentration leaves of 'Joker' plants had significantly lower antioxidant capacity and higher malondialdehyde (MDA, an indicator of lipid peroxidation) level than 'Oitol'. According to RT-qPCR transcript levels of several antioxidant enzymes' genes (ascorbate peroxidase, glutathione reductase and glutathione peroxidase) were significantly higher in 'Joker' compared to 'Oitol'. At increased HG concentrations (1.0, 1.5, 2.0, and 2.5 × HG) growth didn't change significantly in either hybrid. Osmotic potential declined at higher fertigation levels. Antioxidant capacity increased in both hybrids with strong characteristic differences favouring 'Oitol' plants. Higher MDA content of leaves testified more oxidative burden in 'Joker' plants at all and especially at the more concentrated HG treatments. This trend was also approved by results of bio photon emission imaging, which is a powerful method to quantify stress level in living tissues with autoluminescence detection technology. Gene expression for antioxidant enzymes followed HG concentration-dependent increase in both hybrids, at a substantially higher level in 'Joker'. Expression of the dehydrin gene DHN3 was preferentially induced at elevated fertigation levels in 'Oitol' plants, which could contribute to the lower oxidative stress detected in this hybrid. Results presented in this report demonstrate differences in shoot growth, antioxidant capacity, level of oxidative stress and antioxidant gene expression in two contrasting cucumber hybrids at basal fertigation. Furthermore, excessive HG fertigation was found to increase oxidative stress in a genotype-specific way. This effect may be due to different antioxidant capacity and differential expression of stress protective genes, such as the DHN3 dehydrin.

Cold stress signalling in female reproductive tissues

Cold stress is a significant threat for plant productivity and impacts on plant distribution and crop production, particularly so when it occurs during the growth phase. A developmental stage at risk is that of flowering, since a single stress event during sensitive stages, such as the full-bloom stage of fruit trees can be fatal for reproductive success. Although pollen development and fertilization are widely viewed as the most critical reproductive phases, the development and function of female reproductive tissues, which in Angiosperms are embedded in the gynoecium, are also affected by cold stress. Today however, we have essentially no understanding of the cold stress response pathways that act during floral organogenesis. In this review, we briefly summarize our current knowledge of cold stress signalling modules active in vegetative tissues that may provide a framework of general principles also transferable to female reproductive tissues. We then align these signalling cascades with those that govern gynoecium development to identify factors that may act in both processes and could thereby contribute to cold stress responses in female reproductive tissues.