TheArabidopsisC2H2 Zinc Finger INDETERMINATE DOMAIN1/ENHYDROUS Promotes the Transition to Germination by Regulating Light and Hormonal Signaling during Seed Maturation

Abstract

Seed development ends with a maturation phase that imparts desiccation tolerance, nutrient reserves, and dormancy degree. Here, we report the functional analysis of an Arabidopsis thaliana C2H2 zinc finger protein INDETERMINATE DOMAIN1 (IDD1)/ENHYDROUS (ENY). Ectopic expression of IDD1/ENY (2x35S:ENY) disrupted seed development, delaying endosperm depletion and testa senescence, resulting in an abbreviated maturation program. Consequently, mature 2x35S: ENY seeds had increased endosperm-specific fatty acids, starch retention, and defective mucilage extrusion. Using RAB18 promoter ENY lines (RAB18:ENY) to confine expression to maturation, when native ENY expression increased and peaked, resulted in mature seed with lower abscisic acid (ABA) content and decreased germination sensitivity to applied ABA. Furthermore, results of far-red and red light treatments of 2x35S:ENY and RAB18:ENY germinating seeds, and of artificial microRNA knockdown lines, suggest that ENY acts to promote germination. After using RAB18:ENY seedlings to induce ENY during ABA application, key genes in gibberellin (GA) metabolism and signaling were differentially regulated in a manner suggesting negative feedback regulation. Furthermore, GA treatment resulted in a skotomorphogenic-like phenotype in light-grown 2x35S:ENY and RAB18:ENY seedlings. The physical interaction of ENY with DELLAs and an ENYtriggered accumulation of DELLA transcripts during maturation support the conclusion that ENY mediates GA effects to balance ABA-promoted maturation during late seed development.

Gibberellin signaling in plants

“…Meanwhile, GA relieves the repression of the DELLAs by promoting their degradation via the 26S proteasome pathway. More recently, DELLAs have been shown to interact with and inhibit the activity of numerous transcription regulators (Cheminant et al, 2011;Feurtado et al, 2011;Josse et al, 2011;Hong et al, 2012;An et al, 2012;Zhang et al, 2011). By doing so, GA signaling controls the expression of a multitude of target genes functioning in distinct pathways.…”

Regulatory modules controlling maize inflorescence architecture

“…RA1 and KN1 co-occupied the same site in the promoter of another IDD gene, an ortholog of LOOSE PLANT ARCHITECTURE 1, which regulates tiller angle in rice ), but loss of kn1 function did not alter its expression. RA1 (Feurtado et al 2011). Evidence for combinatorial action of IDD genes in developmental patterning has recently emerged (Welch et al 2007;Reinhart et al 2013;Slewinski 2013), including novel roles in lateral organ development via regulation of auxin biosynthesis and transport (Cui et al 2013).…”

A Gibberellin-Mediated DELLA-NAC Signaling Cascade Regulates Cellulose Synthesis in Rice

“…These interactions integrate GA with various signals for coordinated regulation of plant growth and defense (Hou et al, 2010;Bai et al, 2012). Although studies of recently identified DELLA-interacting proteins have revealed the mechanisms of several GA-mediated responses (Arnaud et al, 2010;Cheminant et al, 2011;Feurtado et al, 2011;Yu et al, 2012;Marín-de la Rosa et al, 2014), much work is required to obtain a clear understanding of the numerous roles played by GA.…”