Shade-Inducible Gene Expression Change in <i>Arabidopsis thaliana</i> at Different Temperatures

Abstract

We tested whether the plant response to an environmental factor could be affected by the context of another factor by using shade avoidance response at different temperatures. Depleting the red light (R; λ max = 660 nm) and/or enriching the far-red light (FR; λ max = 730 nm) results in a low R:FR ratio in the environment, which induces shade avoidance response such as elongation of petioles and reduction of plant pigments. On the other hand, warmer environmental temperature is known to mimic shade avoidance response under normal light condition, suggesting a potential crosstalk between the temperature and the light quality signals. Therefore, we investigated the patterns of gene expression responses to low R:FR ratio in different temperature contexts (22°C and 26°C) through microarray analyses. Similar, yet distinct patterns between the two responses were implicated by the levels of correlation in the commonly affected MapMan bins. However, the induction levels of typical shade genes such as ATHB2 , IAA29 , IAA19 , HFR1 , YUC8 , and FT were very similar at both temperatures. Moreover, petiole length, chlorophylls, carotenoids, and anthocyanins contents did not support any statistically significant interaction between the light quality and the high temperature responses despite the obvious independent effect of each signal, which suggests cumulative effects of two independent responses. Nevertheless, other types of low R: FR-responsive genes with differential expression patterns at different temperatures were identified. They are overrepresented in secondary metabolism, lipid transport, oxidative stress, jasmonic acid, ethylene, light, pathogen defense responses, and extracellular region.