Deregulation of ζ‐carotene desaturase in Arabidopsis and tomato exposes a unique carotenoid‐derived redundant regulation of floral meristem identity and function

Abstract

A level of redundancy and interplay among the transcriptional regulators of floral development safeguards a plant's reproductive success and ensures crop production. In the present study, an additional layer of complexity in the regulation of floral meristem (FM) identity and flower development is elucidated linking carotenoid biosynthesis and metabolism to the regulation of determinate flowering. The accumulation and subsequent cleavage of a diverse array of f-carotenes in the chloroplast biogenesis 5 (clb5) mutant of Arabidopsis results in the reprogramming of meristematic gene regulatory networks establishing FM identity mirroring that of the FM identity master regulator, APETALA1 (AP1). The immediate transition to floral development in clb5 requires long photoperiods in a GIGANTEA-independent manner, whereas AP1 is essential for the floral organ development of clb5. The elucidation of this link between carotenoid metabolism and floral development translates to tomato exposing a regulation of FM identity redundant to and initiated by AP1 and proposed to be dependent on the E class floral initiation and organ identity regulator, SEPALLATA3 (SEP3).

Reducing PSY activity fine tunes threshold levels of acis-carotene-derived signal that regulates the PIF3/HY5 module and plastid biogenesis

“…Yet to be identified apocarotenoids can also be derived from acyclic linear cis-carotenes herein referred to as a cis-apocarotenoid signal (cis-ACS) (Alagoz et al, 2018;Anwar et al, 2021). Mutations in the Arabidopsis ZDS lead to the accumulation of phytofluene and ζ-carotene isomers that, via CCD4 cleavage, trigger a cis-ACS regulating PHOTOSYNTHESIS ASSOCIATED NUCLEAR GENE (PhANG) expression and chloroplast translation that leads to impaired chloroplast biogenesis, cellular differentiation and disruptions in leaf and flower meristem identity (Avendano-Vazquez et al, 2014;Escobar-Tovar et al, 2021;McQuinn et al, 2023). A cis-ACS likely derived from di-cis-ζ-carotene, neurosporene, and/or prolycopene produced by the loss-of-function in crtiso ziso double mutants was shown to regulate PhANG expression and plastid development during skotomorphogenesis (e.g., formation of the prolamellar body; PLB) and photomorphogenesis (e.g., thylakoid structures within the chloroplast) (Cazzonelli et al, 2020).…”