Towards a tailored indoor horticulture:a functional genomics guided phenotypic approach

As indoor horticulture gathers momentum,electric(also termed artificial)lighting systems with the ability to generate specific and tunable wavelengths have been developed and applied.While the effects of light quality on plant growth and development have been studied,authoritative and reliable sets of light formulae tailored for the cultivation of economically important plants and plant traits are lacking as light qualities employed across laboratories are inconsistent.This is due,at least in part,to the lack of molecular data for plants examined under electric lights in indoor environments.It has hampered progress in the field of indoor horticulture,in particular,the transition from small-scale indoor farming to commercial plant factories.Here,we review the effects of light quality on model and crop plants studied from a physiological,physical and biochemical perspective,and explain how functional genomics can be employed in tandem to generate a wealth of molecular data specific for plants cultivated under indoor lighting.We also review the current state of lighting technologies in indoor horticulture specifically discussing how recent narrow-bandwidth lighting technologies can be tailored to cultivate economically valuable plant species and traits.Knowledge gained from a complementary phenotypic and functional genomics approach can be harvested not only for economical gains but also for sustainable food production.We believe that this review serves as a platform that guides future light-related plant research.

Adenylate cyclase activity of TIR1/AFB links cAMP to auxin-dependent responses

The phytohormone auxin is essential for plant growth and development as well as cellular and systemic responses to environmental cues.The auxin receptor TRANSPORT INHIBITOR RESPONSE 1/AUXIN-SIGNALING F-BOX(TIR1/AFB)lies within an E3 ubiquitin ligase complex(SCF^(TIR1/AFB))consisting of Skp,Cullin,and F-box proteins.Auxin brings together TIR1/AFB and the transcriptional repressor Auxin/INDOLE-3-ACETIC ACID(Aux/IAA),which allows the SCF^(TIR1/AFB) complex to transfer activated ubiquitin to Aux/IAA,thereby targeting it for proteasomal degradation.This liberates the transcription factors AUXINRESPONSE FACTORs for auxin-dependent transcription(Lavy and Estelle,2016).

Identification of potential nitric oxide-sensing proteins using the H-NOX motif

NO Sensing Is Universal and Ancient During the anoxic stages of the early Earth,nitric oxide(NO)served as a major nitrogen source for prokaryotes,which,against a backdrop of an increasingly oxygen-rich atmosphere,evolved NO signaling mechanisms for processes including the regulation of communal behavior(Plate and Marietta,2012).In humans,NO lowers blood pressure,acts as neurotransmitter,and activates macrophages during immune responses(Farah et al.,2018).Animal NO-sensing proteins share structural similarity with those of early prokaryotes,as exemplified by the activation of soluble guanylate cyclases(sGCs),in which a heme-containing domain enables NO sensing by the heme NO/oxygen(H-NOX),thus indicating ancient evolutionary origin.In plants,NO signals for defense,growth,and developmental processes(Durner et al.,1998;Domingos et al.,2015)appeared to occur mainly through protein S-nitrosation,where the redox changes of sensing proteins could directly modulate enzymatic activities thereby causing the release of reactive oxygen intermediates,or by alteration of methylation patterns of defense genes that,in turn,affect programmed cell death during stress responses(Tada et al.,2008;Yun et al.,2011;Hu et al.,2017).