Differentially Phased Leaf Growth and Movements in Arabidopsis Depend on Coordinated Circadian and Light Regulation

Abstract

In contrast to vastly studied hypocotyl growth, little is known about diel regulation of leaf growth and its coordination with movements such as changes in leaf elevation angle (hyponasty). We developed a 3D live-leaf growth analysis system enabling simultaneous monitoring of growth and movements. Leaf growth is maximal several hours after dawn, requires light, and is regulated by daylength, suggesting coupling between growth and metabolism. We identify both blade and petiole positioning as important components of leaf movements in Arabidopsis thaliana and reveal a temporal delay between growth and movements. In hypocotyls, the combination of circadian expression of PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 and their light-regulated protein stability drives rhythmic hypocotyl elongation with peak growth at dawn. We find that PIF4 and PIF5 are not essential to sustain rhythmic leaf growth but influence their amplitude. Furthermore, EARLY FLOWERING3, a member of the evening complex (EC), is required to maintain the correct phase between growth and movement. Our study shows that the mechanisms underlying rhythmic hypocotyl and leaf growth differ. Moreover, we reveal the temporal relationship between leaf elongation and movements and demonstrate the importance of the EC for the coordination of these phenotypic traits.

Local auxin production underlies a spatially restricted neighbor-detection response in Arabidopsis

“…1A and Fig. S2 B-D) (31). Moreover, a reduction of the R/FR led to a strongly reduced leaf hyponastic response in pif4pif5pif7 and pif7 mutants, indicating that the low R/FR-controlled leaf position is predominantly regulated by PIF7 (Fig.…”

“…leaf position (tip elevation angle) with high spatial and temporal resolution in plants growing in control (high R/FR) and low R/FR (simulated neighbors) conditions using previously described methodology (31). We typically monitored leaves 1 and 2, which are at the same developmental stage, but similar response patterns were observed in younger leaves ( Fig.…”

“…1 and Fig. S1 A and B) (31). A photogrammetric approach showed that tip and petiole elevation angles are highly correlated, justifying the choice of tip position as a proxy for leaf movement (Fig.…”

A Journey Through a Leaf: Phenomics Analysis of Leaf Growth inArabidopsis thaliana

“…With this high temporal resolution of imaging, additional observations can be made, such as diurnal movements of the rosette leaves. These changes of the leaf elevation angle, known as hyponasty, are influenced by temperature (Vile et al, 2012), circadian rhythm and light conditions (Dornbusch et al, 2014), and can be measured using laser scanning techniques (Dornbusch et al, 2012) or by combining focused and depth images of the rosette (Apelt et al, 2015).…”

The lost art of looking at plants

“…Some are now able to collect data about plant architecture, such as branching and leaf shape, using laser scanners and depth sensors. Similar scanners have been used in lab-grown plants to analyse the rhythmic growth of leaves, and to link that growth to a particular protein complex 3 .…”