Time-Series Transcriptomics Reveals That AGAMOUS-LIKE22 Affects Primary Metabolism and Developmental Processes in Drought-Stressed Arabidopsis

Abstract

In Arabidopsis thaliana, changes in metabolism and gene expression drive increased drought tolerance and initiate diverse drought avoidance and escape responses. To address regulatory processes that link these responses, we set out to identify genes that govern early responses to drought. To do this, a high-resolution time series transcriptomics data set was produced, coupled with detailed physiological and metabolic analyses of plants subjected to a slow transition from well-watered to drought conditions. A total of 1815 drought-responsive differentially expressed genes were identified. The early changes in gene expression coincided with a drop in carbon assimilation, and only in the late stages with an increase in foliar abscisic acid content. To identify gene regulatory networks (GRNs) mediating the transition between the early and late stages of drought, we used Bayesian network modeling of differentially expressed transcription factor (TF) genes. This approach identified AGAMOUS-LIKE22 (AGL22), as key hub gene in a TF GRN. It has previously been shown that AGL22 is involved in the transition from vegetative state to flowering but here we show that AGL22 expression influences steady state photosynthetic rates and lifetime water use. This suggests that AGL22 uniquely regulates a transcriptional network during drought stress, linking changes in primary metabolism and the initiation of stress responses.

Accelerated flowering time reduces lifetime water use without penalizing reproductive performance in Arabidopsis

“…Investigating the natural variation in whole‐plant WUE and the mechanisms of drought resistance in natural populations is challenging, due to difficulties in recreating realistic drought conditions in an experimental setting. For example, in short‐dehydration experiments (Bechtold et al, , ; Ferguson, Humphry, Lawson, Brendel, & Bechtold, ), water loss is greater in larger plants creating substantial heterogeneity in the timing of water deficits (Kooyers, ). Although plant size greatly contributes to water loss in Arabidopsis, drought response traits are independent of the transpiring leaf surface (Ferguson et al, ).…”

Drought stress differentially regulates the expression of small open reading frames (sORFs) in Arabidopsis roots and shoots

“…A water content around 38% and 15% has been reported on the 8 th and 13 th day of drought stress in normal soil, respectively. 18 Root and shoot fresh weight increased up to the fifth day of the drought stress, and then began to drop by the seventh day (Fig. 1B).…”

Fundamental and applied research in ABA signaling: Regulation by ABA of the chromatin remodeling ATPase BRAHMA and biotechnological use of the PP2CA promoter.

“…In response to ABA, more than 10% of the transcriptome is modified indicating that, high plasticity of the genome is needed to allow genes to be activated or repressed by this hormone , Bechtold et al, 2016. Chromatin-remodeling activity in plants plays an essential role to sustain these massive changes in gene expression providing the necessary flexibility for developmental plasticity and stress adaptation (Jarillo et al, 2009, Ahmad et al, 2010, Weake & Workman, 2010.…”

“…ABA plays major roles in abiotic and biotic stress responses. It is implicated in guard cell regulation triggering stomatal closure to maintain water balance (Sirichandra et al, 2009, Merilo et al, 2015, Munemasa et al, 2015, antagonizes gibberellins (GAs) effects to fine tune growth in adverse situations (Golldack et al, 2013), controls gene expression to help with plant adaptation to stress (Bechtold et al, 2016) and also has a role in the promotion of plant resistance to pathogens restricting its entrance via stomata (McLachlan et al, 2014). Despite of the well known functions in abiotic and biotic stress, ABA is also important for the regulation of several physiological and developmental events as embryo maturation, promotion of seed desiccation tolerance and dormancy, germination and seedling establishment, primary and lateral root growth and transition from vegetative to reproductive stage (Finkelstein et al, 2002, Cutler et al, 2010, Finkelstein, 2013, Harris, 2015.…”

“…At cellular level, plants respond to drought with changes in gene expression and protein and metabolite abundances, which are part of the defense mechanisms (Bechtold et al, 2016).…”