The nitrogen-fixing symbiotic cyanobacterium,Nostoc punctiformecan regulate plant programmed cell death

Abstract

Cyanobacteria such as Nostoc spp. can form nitrogen-fixing symbioses with a broad range of plant species. Unlike other plant-bacteria symbioses, little is understood about the immunological and developmental signalling events induced by Nostoc cyanobionts (symbiotic cyanobacteria). Here, we used suspension cell cultures to elucidate the early molecular mechanisms underpinning the association between cyanobionts and plants by studying the effects of conditioned medium (CM) from Nostoc punctiforme cultures on plant programmed cell death (PCD), a typical immune response activated during incompatible interactions. We showed that N. punctiforme-CM could suppress PCD induced by a temperature stress. Interestingly, this was preceded by significant transcriptional reprogramming, as evidenced by the differential regulation of a network of defence-associated genes, as well as genes implicated in regulating cell growth and differentiation. This work is the first to show that cyanobionts can regulate PCD in plants and provides a valuable transcriptome resource for the early immunological and developmental signalling events elicited by Nostoc cyanobionts.

Early events of the endophytic symbiotic betweenOryza sativaandNostoc punctiformeinvolve the SYM pathway

“…Our proteomic analysis revealed the expression in response to Nostoc of three GST enzymes. It has been shown recently that N. punctiforme induces the expression of GST enzymes in Arabidopsis to reduce toxic ROS and limit the extent of the hypersensitive response (Belton et al, 2020). A protein with a Gnk2-homologous domain was also significantly induced in Oryza in response to Nostoc .…”

“…Very little is known about the plant changes in response to the cyanobacterium. Expression changes in response to Nostoc have been studied by RNA-seq in Anthoceros and Arabidopsis (Li et al, 2020; Belton et al, 2020). Activation of receptor kinases and genes involved in stress response have been reported.…”