Enhanced seedling growth by 3‐n‐pentadecylphenolethanolamide is mediated by fatty acid amide hydrolases in upland cotton (Gossypium hirsutum L.)

Abstract

Fatty acid amide hydrolase (FAAH) is a conserved amidase that is known to modulate the levels of endogenous N-acylethanolamines (NAEs) in both plants and animals. The activity of FAAH is enhanced in vitro by synthetic phenoxyacylethanolamides resulting in greater hydrolysis of NAEs. Previously, 3-npentadecylphenolethanolamide (PDP-EA) was shown to exert positive effects on the development of Arabidopsis seedlings by enhancing Arabidopsis FAAH (AtFAAH) activity. However, there is little information regarding FAAH activity and the impact of PDP-EA in the development of seedlings of other plant species. Here, we examined the effects of PDP-EA on growth of upland cotton (Gossypium hirsutum L. cv Coker 312) seedlings including two lines of transgenic seedlings overexpressing AtFAAH. Independent transgenic events showed accelerated true-leaf emergence compared with non-transgenic controls. Exogenous applications of PDP-EA led to increases in overall seedling growth in AtFAAH transgenic lines. These enhancedgrowth phenotypes coincided with elevated FAAH activities toward NAEs and NAE oxylipins. Conversely, the endogenous contents of NAEs and NAE-oxylipin species, especially linoleoylethanolamide and 9-hydroxy linoleoylethanolamide, were lower in PDP-EA treated seedlings than in controls. Further, transcripts for endogenous cotton FAAH genes were increased following PDP-EA exposure. Collectively, our data corroborate that the enhancement of FAAH enzyme activity by PDP-EA stimulates NAE-hydrolysis and that this results in enhanced growth in seedlings of a perennial crop species, extending the role of NAE metabolism in seedling development beyond the model annual plant species, Arabidopsis thaliana.

Fatty acid amide hydrolase and 9-lipoxygenase modulate cotton seedling growth by ethanolamide oxylipin levels

“…Recently, six FAAH homologs to the Arabidopsis FAAH (AtFAAH) gene were identified and clustered into two groups; FAAH I (GhFAAH Ia, Ib, and Ic) and FAAH II (GhFAAH IIa, IIb, and IIc) ( Arias-Gaguancela et al, 2022 ). However, their physiological role was not explored further.…”

“…There is the possibility that these FAAHs may have overlapping functionality towards certain NAEs, while being distinct towards other lyophilic substrates. In upland cotton ( Gossypium hirsutum L.), six GhFAAHs were reported previously ( Arias-Gaguancela et al, 2022 ). FAAH group I is composed of GhFAAH Ia , Ib , Ic , and these clustered with AtFAAH , whereas GhFAAH IIa , IIb , and IIc are part of FAAH group II .…”

“…FAAH group I is composed of GhFAAH Ia , Ib , Ic , and these clustered with AtFAAH , whereas GhFAAH IIa , IIb , and IIc are part of FAAH group II . Group I had higher levels of expression in cotton tissues compared with group II, but all FAAHs were expressed in multiple tissues with somewhat greater expression in seedlings and mature leaves ( Arias-Gaguancela et al, 2022 ).…”

“…These findings suggest that the elevated amount of AtFAAH in Arabidopsis transgenics promoted a rapid degradation of NAEs, and this was accompanied by enhanced tolerance to inhibitory growth effects of NAEs. Similarly, transgenic cotton seedlings with ectopic expression of AtFAAH exhibited tolerance to exogenously applied NAEs ( Arias-Gaguancela et al, 2022 ).…”

“…Hence it is unclear if, or how, the interplay between FAAH and LOX enzymes might influence seedling development in more complex systems. For example, cotton has a total of six FAAH genes (three group I and three group II) ( Arias-Gaguancela et al, 2022 ) and 21 LOX genes (six putative 9-LOXes and 15 putative13-LOXes, grouped in two sub families; type I and II) ( Shaban et al, 2018 ). Here, we utilized virus-induced gene silencing (VIGS) to suppress multiple cotton FAAH and/or 9-LOX isoforms to assess their impact in seedling growth and NAE oxylipin metabolism.…”