In-Cold Exposure to Z-3-Hexenal Provides Protection Against Ongoing Cold Stress in Zea mays

Abstract

Green leaf volatiles (GLVs), which have mostly been described as providers of protection against insect herbivory and necrotrophic pathogen infections, were recently shown to provide significant fortification against cold stress damage. It was further demonstrated that cold-damaged maize seedlings released a significant amount of GLVs, in particular, Z-3-hexenal (Z-3-HAL). Here, we report that the in-cold treatment of maize seedlings with Z-3-HAL significantly improved cold stress resistance. The transcripts for cold-protective genes were also significantly increased in the Z-3-HAL treated maize seedlings over those found in only cold stressed plants. Consequently, the maize seedlings treated with HAL during cold showed a significantly increased structural integrity, significantly less damage, and increased growth after cold stress, relative to the non-HAL treated maize seedlings. Together, these results demonstrate the protective effect of in-cold treatment with HAL against cold damage, and suggest that the perception of these compounds during cold episodes significantly improves resistance against this abiotic stress.

Keywords: Z-3-hexenal; Zea mays; abiotic stress; cold protection; cold stress; green leaf volatiles; ion leakage.

Figure 1

Release of green leaf volatiles from cold stress damaged maize (Zea mays) seedlings. Maize seedlings were either placed at −5 °C or at room temperature (RT), and volatiles were collected for 1 h (n = 4). Values are means ± standard deviation (SD), and asterisks indicate significant differences between treated and untreated seedlings (t-test, p < 0.05; n.d., not detectable).

Figure 2

The effect of in-cold (Z)-3-hexen-1-al (Z-3-HAL) treatment on cold stress related gene expression in maize (Zea mays) seedlings (n = 3) under cold stress (5 °C). Seedlings were treated with physiological concentrations of Z-3-HAC (20 μg L⁻¹) 30 min after being placed at 5 °C for 90 min and 180 min. Transcript levels were measured by RT-qPCR. The values are means ± standard error of the mean (SEM), and the asterisks indicate significant differences between the treated and untreated seedlings (t-test, p < 0.05).

Figure 3

The effect of in-cold (Z)-3-hexen-1-al (Z-3-HAL) treatment on cold stress related ion leakage in maize (Zea mays) seedlings (n = 6). The relative conductivity is expressed as the ratio between ion leakage after short cold stress, divided by the total ion leakage after overnight freezing and thawing. The values are means ± SD, and different letters indicate significant differences between the treated and untreated seedlings (ANOVA, p < 0.05).

Figure 4

The effect of in-cold (Z)-3-hexen-1-al (Z-3-HAL) treatment on damage in maize (Zea mays) seedlings. Assessment of damage on a scale from 0 (no damage) to 4 (dead). The values are means ± SD, and the asterisks indicate significant differences between the treated and untreated seedlings (Students t-test, p < 0.05).

Figure 5

The growth response of in-cold (Z)-3-hexen-1-al (Z-3-HAL) and untreated maize (Zea mays) seedlings (n = 6) after 16 h at 5 °C and at room temperature (RT). Growth is expressed in relative units, with the RT control plants set at 100% for the observed growth period. The values are means ± SD, and the different letters indicate significant differences (ANOVA, p < 0.05).