Two hybrid histidine kinases, TcsB and the phytochrome FphA, are involved in temperature sensing in Aspergillus nidulans

Abstract

Summary The adaptation of microorganisms to different temperatures is an advantage in habitats with steadily changing conditions and raises the question about temperature sensing. Here we show that in the filamentous fungus Aspergillus nidulans, the hybrid histidine kinase TcsB and phytochrome are involved in temperature‐induced gene transcription. Temperature‐activated phytochrome fed the signal into the HOG MAP kinase pathway. There is evidence that the photoreceptor phytochrome fulfills a temperature sensory role in plants and bacteria. The effects in plants are based on dark reversion from the active form of phytochrome, Pfr, to the inactive form, Pr. Elevated temperature leads to higher dark reversion rates, and hence, temperature sensing depends on light. In A. nidulans and in Alternaria alternata, the temperature response was light‐independent. In order to understand the primary temperature response of phytochrome, we performed spectral analyses of recombinant FphA from both fungi. Spectral properties after heat stress resembled the spectrum of free biliverdin, suggesting conformational changes and a softening of the binding pocket of phytochrome, possibly mimicking photoactivation. We propose a novel function for fungal phytochrome as temperature sensor.

Phytochromes in Agrobacterium fabrum

“…If phytochrome would act in darkness, then a phytochrome mutant should have a phenotype in the dark, which is usually not the case ( Dehesh et al, 1993 ). The results of A. fabrum show that these phytochromes can be active in darkness and in the light, a feature also found for fungal phytochromes ( Yu et al, 2019 ).…”

A light life together: photosensing in the plant microbiota

“…Most interestingly and indicative of FphA photochromicity and activity is the fact that RL-induced conidiation is reversed by FRL [116,117]. FphA is also involved in temperature, osmolarity, and stress sensing signalling [118,119]. Through FphA, light upregulates NO levels and the expression of agaA (arginase) and fhbB (flavohaemoglobin B) [120].…”

“…LerA favours sexual reproduction [115] BL, RL and FRL delay conidiospore germination [118] WL represses production of the mycotoxin sterigmatocystin; FphA inhibitor, LreA stimulator [115] FphA involved in temperature sensing, osmosensing and stress-sensing signalling [118,119] WL upregulates NO; FphA upregulates and LreA represses agaA and fhbB a . The global nuclear regulator RlcA interacts with FphA [121] FphA LreA (WC-1),…”

Aspergillus fumigatus biofilms: Toward understanding how growth as a multicellular network increases antifungal resistance and disease progression

“…In A . nidulans , temperature is sensed by TcsB and FphA, where FphA modulates the expression of many downstream genes via the HOG signaling pathway [ 22 ]. RasA and cAMP mediated signaling initiate conidial swelling in response to carbon sources in A .…”