The 30th International Conference on Arabidopsis Research (ICAR 2019)

407 / 2018-12-14 19:27:48

High ambient temperature antagonizes ethylene-induced exaggerated apical hook formation in etiolated Arabidopsis seedlings

Ethylene,thermomorphogenesis,,auxin

Plenary track > Hormones

It is well established that high ambient temperature induces cell elongation in light-grown Arabidopsis thaliana seedlings by stimulating auxin production. However, how etiolated seedlings respond to elevated ambient temperature is still elusive. Here, we show that in darkness, high ambient temperature suppresses the ethylene-triggered exaggerated hook formation in wild-type plants and reduces the hook curvatures in constitutively ethylene responsive mutants. We find that high temperature does not affect the activity of the central transcription factor EIN3. Apical hook formation by ethylene is a result of asymmetric auxin distribution, which causes the differential cell elongation. We show that the natural auxin (indole-3-acetic acid, IAA) levels in the hook regions are reduced and their asymmetric distributions are disturbed upon high temperature treatment. Increasing auxin concentrations or blocking auxin transport causes seedlings insensitive to high temperature, supporting that adequate local auxin activity is required for thermo-sensory hook development. Next, we monitor the transcription of several genes encoding auxin biosynthesis related enzymes and find that most YUCCA genes are transcriptionally down-regulated by elevating temperature. Taken together, we demonstrate that high temperature suppresses ethylene-induced exaggerated hook formation via the inhibition of local auxin activities.