AMP1 and CYP78A5/7 act through a common pathway to govern cell fate maintenance in Arabidopsis thaliana

Abstract

Higher plants can continuously form new organs by the sustained activity of pluripotent stem cells. These stem cells are embedded in meristems, where they produce descendants, which undergo cell proliferation and differentiation programs in a spatiotemporally-controlled manner. Under certain conditions, pluripotency can be reestablished in descending cells and this reversion in cell fate appears to be actively suppressed by the existing stem cell pool. Mutation of the putative carboxypeptidase ALTERED MERISTEM PROGRAM1 (AMP1) in Arabidopsis causes defects in the suppression of pluripotency in cells normally programmed for differentiation, giving rise to unique hypertrophic phenotypes during embryogenesis as well as in the shoot apical meristem. A role of AMP1 in the miRNAdependent control of translation has recently been established, however, how this activity is connected to its developmental functions is not resolved. Here we identify members of the cytochrome P450 clade CYP78A to act in parallel with AMP1 to control cell fate in Arabidopsis. Mutation of CYP78A5 and its close homolog CYP78A7 in a cyp78a5,7 double mutant caused suspensor-to-embryo conversion and ectopic stem cell pool formation in the shoot meristem, phenotypes characteristic for amp1. The tissues affected in the mutants showed pronounced expression levels of AMP1 and CYP78A5 in wild type. A comparison of mutant transcriptomic responses revealed an intriguing degree of overlap and highlighted alterations in protein lipidation processes. Moreover, we also found elevated protein levels of selected miRNA targets in cyp78a5,7. Based on comprehensive genetic interaction studies we propose a model in which both enzyme classes act on a common downstream process to sustain cell fate decisions in the early embryo and the shoot apical meristem.

Plant cytochrome P450 plasticity and evolution

“…Some conifer-specific CYP720Bs, however, oxygenate several diterpene backbones (Ro et al, 2005;Hamberger et al, 2011;Geisler et al, 2016), which might constitute a lead to the family activity in hormone metabolism. The functions of CYP78s that were already known to control organ growth have been extended to cell fate maintenance and control of defense against a broad spectrum of pathogens, still without identification of the signal generated (Maeda et al, 2019;Poretska et al, 2020).…”

Evolutionary and Functional Characterization of Cytochrome P450 in Cotton Reveal the Role of Subgenome Expression of GhCYP78A for Cotton Fiber Initiation

“…5A) also reproducing our previous result [54]. In plants, different CYP78A viz., CYP78A5 (KLUH), CYP78A6 (EOD3) and CYP78A7 (PLA1) were functionally characterized for different organ development, cell fate determining and differentiation processes that possibly worked downstream to the GA [12][13][14]52,[55][56][57][58][59][60]. In cotton, the GhKLUH-like (EOD3), GhKLUH and GhPLA1 clades were clustered under group I, group IV and group VIII respectively that postulated their functional conservation (Fig.…”

“…CYP78A causing endoreduplication and cell proliferation associated with the fruit size and seed size and their weight which ultimately increases the biomass and yield in many crops [12][13][14]52,55,56,59].…”

Regulation of the plastochron by three many-noded dwarf genes in barley

“…The pla1 , pla2 , and pla3 mutants have a short plastochron and a small leaf size, and conversion of the primary rachis into a shoot occurs in all three, but it has been proposed that PLA1 , PLA2 , and PLA3 regulate the plastochron independently [ 7 , 9 ]. On the other hand, Arabidopsis AMP1 and CYP78A5/7 , which are orthologs of PLA3 and PLA1 , respectively, act on a common downstream process [ 42 ].…”