NITRIC OXIDE REGULATION OF SEED LIPID ACCUMULATION INVOLVES bZIP REVERSIBLE S-NITROSYLATION
Sánchez-Vicente, I.1, Albertos, P.2, Mateos, I.1, Sanz, C.3 and Lorenzo, O.1
1Department of Botany and Plant Physiology, Spanish-Portuguese Agricultural Research Institute (CIALE), School of Biology, University of Salamanca, Salamanca, Spain
2Biotechnology of Horticultural Crops, TU München, Freising, Germany
3Department Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa-CSIC, Campus Universidad Pablo de Olavide, Sevilla, Spain
Contact: Inmaculada Sánchez-Vicente, firstname.lastname@example.org
Nitric oxide (NO) is a signalling molecule involved in a plethora of physiological events along the whole plant life, related not only to growth and developmental processes, but also to biotic and abiotic stresses. Our work is focused on early plant development, including seed maturation, dormancy and germination where some members of the basic region/leucine zipper motif (bZIP) transcription factor family are key regulators. We get new insights in the study of these early plant development stages through the NO molecular mechanisms involved in bZIP regulation. NO exerts its function mainly through S-nitrosylation, defined as the specific posttranslational modification by which NO is attached covalently to a cysteine residue, modifying the protein properties. We analyzed the repercussion of this important modification in specific bZIP targets involved in seed development and germination.
Our results show a fundamental NO involvement in the regulation of the proper seed maturation, taking part in seed fatty acid accumulation and promotion of seed germination. We find that accumulation of major fatty acid storage compounds is impaired in different NO mutant backgrounds and also in gain- and loss-of-function lines of the bZIPs analyzed.
Additionally, NO function in embryo fatty acid storage regulation involves the specific and reversible S-nitrosylation of a basic/leucine zipper transcription factor bZIP, which in turns can activate the expression of the FAD3 desaturase. This bZIP is the closest homolog of ABI5, previously characterize as a key seed germination repressor, whose protein stability is also modified by S-nitrosylation. A search of in planta protein interactors of these bZIPs led the identification of specific redoxins among other partners. Likewise, this posttranslational modification can also be reversed by the denitrosylation activity of these redoxins, suggesting a novel and reversible mechanism of bZIP regulation. These results led us to understand the NO control of seed fatty acid profile during maturation and germination.