Shade-avoidance responses become more aggressive in warm environments

Abstract

<jats:title>Abstract</jats:title><jats:p>When exposed to neighbour signals, competitive plants increase the growth of the stem to reduce the degree of current or future shade. Plants can experience similar neighbour cues under different weather conditions and the aim of this work is to investigate the impact of daily average temperature and irradiance and thermal amplitude on the magnitude of shade-avoidance responses in <jats:italic>Arabidopsis thaliana</jats:italic>. For this purpose, we first generated a growth database and elaborated under controlled conditions a model that predicts hypocotyl growth during the photoperiod as a function of the light-modulated activity of the main photo-sensory receptors (phytochromes A and B, cryptochromes 1 and 2), temperature-modulated activity of phytochrome B and an independent temperature input. Thermal amplitude (lower temperatures during the morning and afternoon that at midday) reduced growth of genotypes with normally fast morning growth, and this effect was incorporated to the model. Thermal amplitude also decreased the abundance of the growth-promoting transcription factor PHYTOCHROME-INTERACTING FACTOR 4. The model predicted growth in the field through different seasons with reasonable accuracy. Then, we used the model in combination with a worldwide dataset of current and future whether conditions. The analysis predicted enhanced shade-avoidance responses as a result of higher temperatures due to the geographical location or global warming. Irradiance and thermal amplitude had no effects. These trends were also observed for our local growth measurements. We conclude that, if water and nutrients do not become limiting, warm environments enhance the shade avoidance response.</jats:p>

Canopy Light Quality Modulates Stress Responses in Plants

“…So, both FR enrichment and elevated temperature can inactivate phyB, thereby activating the core downstream pathways toward shoot elongation and hyponasty (Figure 2D). Importantly, increased temperature induced by global warming is also predicted to strengthen shade avoidance–mediated growth responses (Romero-Montepaone et al., 2019), which stresses the relevance of investigating the connections between different environmental cues to better improve crop quality. If higher temperature would indeed increase shade avoidance responses such as shoot elongation, this exaggerated elongation of non-harvestable organs would probably go at the expense of yield.…”

“…Even though photosynthesis might be impaired, phyB mutants accumulate more sucrose and starch in daytime but have reduced biomass compared with WT, indicating that phytochrome signaling plays a key role in biomass production and carbon resource allocation in Arabidopsis (De Wit et al, 2018;Yang et al, 2016). Interestingly, even though most plant species show a shade avoidance behavior (Roig-Villanova and Martínez-García, 2016), shoot elongation is not always an option. For example, plant species growing under tree canopies can obviously not outgrow the trees (Gommers et al, 2013).…”

“…Plants employ a suite of developmental adjustments to increase their competitive ability, known as the ''shade avoidance syndrome (SAS)'' (Ballaré and Pierik, 2017;Casal, 2013). SAS response is constituted of rapid hypocotyl, internode, and petiole elongation as well as upward movement of leaves (hyponasty), apical dominance and early flowering in Arabidopsis (Casal, 2012;Roig-Villanova and Martínez-García, 2016). Although immense progress has been made in unraveling the molecular mechanisms underpinning different SAS components, the impacts of density light cues and SAS responses on the ability of plants to deal with other challenging conditions such as abiotic and biotic stresses has not been very intensively studied.…”

Functional convergence of growth responses to shade and warmth in Arabidopsis

“…9a). We calculated the activity of the photosensory receptors under the different light or shade conditions (Romero‐Montepaone et al ., 2020). The slope of the linear response to temperature decreased with photosensory receptor activity (Fig.…”

Phytochrome B and PCH1 protein dynamics store night temperature information

“…In these seedlings, warm night temperatures enhance not only growth during the night but also during the subsequent photoperiod, while in seedlings retaining phyB Pfr the enhanced warm night growth is partially compensated by reduced growth the following day. These observations support the notion that thermomorphogenesis is particularly important for enhancing shade avoidance (Romero‐Montepaone et al ., 2020) and hence reduce the double jeopardy imposed on carbon balance by the combination of shade and warmth (Casal and Balasubramanian, 2019).…”