The dehydratase ADT3 affects ROS homeostasis and cotyledon development

Abstract

During the transition from seed to seedling, emerging embryos strategically balance available resources between building up defenses against environmental threats and initiating the developmental program that promotes the switch to autotrophy. We present evidence of a critical role for the phenylalanine (Phe) biosynthetic activity of AROGENATE DEHYDRATASE3 (ADT3) in coordinating reactive oxygen species (ROS) homeostasis and cotyledon development in etiolated Arabidopsis (Arabidopsis thaliana) seedlings. We show that ADT3 is expressed in the cotyledon and shoot apical meristem, mainly in the cytosol, and that the epidermis of adt3 cotyledons contains higher levels of ROS. Genome-wide proteomics of the adt3 mutant revealed a general down-regulation of plastidic proteins and ROS-scavenging enzymes, corroborating the hypothesis that the ADT3 supply of Phe is required to control ROS concentration and distribution to protect cellular components. In addition, loss of ADT3 disrupts cotyledon epidermal patterning by affecting the number and expansion of pavement cells and stomata cell fate specification; we also observed severe alterations in mesophyll cells, which lack oil bodies and normal plastids. Interestingly, up-regulation of the pathway leading to cuticle production is accompanied by an abnormal cuticle structure and/or deposition in the adt3 mutant. Such impairment results in an increase in cell permeability and provides a link to understand the cell defects in the adt3 cotyledon epidermis. We suggest an additional role of Phe in supplying nutrients to the young seedling.

Flexible functional interactions between G‐protein subunits contribute to the specificity of plant responses

“…Intriguingly, adt3 mutants have reduced stomatal density, similar to gpa1 . Exogenous addition of Phe reverted back the adt3 and gpa1 stomatal phenotypes to the WT level, supporting a link between amino acid biosynthesis and G‐protein signaling during stomatal development (Para et al , ). Although it is not known what effect Phe might have on agb1 or xlg1.2.3 stomatal phenotypes, it does suggest the existence of additional non‐canonical pathways.…”

The effects of putrescine are partly overlapping with osmotic stress processes in wheat

“…However unique induction of the genes related to arogenate dehydratase 3, electron transfer flavoprotein ubiquinone oxide reductase (ETFQO), metallothionein 3 and 6-phosphogluconate dehydrogenase decarboxylating 1 was also found after PUT pre-treatment compared to the control and PEG treatment alone. Arogenate dehydratase catalyses the last steps of the biosynthesis of phenylalanine in plants, and its involvement in coordinating the homeostasis of reactive oxygen species and cotyledon development in etiolated Arabidopsis has been recently demonstrated [49]. The essential role of ETFQO in Arabidopsis during long-term dark-induced carbohydrate deprivation has been also reported [50].…”

Control of grain size by G protein signaling in rice

“…Plant genomes do not encode homologs of the well‐studied animal G protein effectors (Pandey and Vijayakumar ). Although a number of interacting factors of G proteins have been identified (Warpeha et al ; Mudgil et al ; Klopffleisch et al ; Hu et al ; Para et al ), none of them have been proven as effectors of G protein signaling.…”