BcAtf1, a global regulator, controls various differentiation processes and phytotoxin production inBotrytis cinerea

Abstract

Atf1-homologous basic region leucine zipper (bZIP) transcription factors are known to act downstream of the stress-activated mitogen-activated protein kinase (SAPK) cascade in mammals, as well as in several fungi; they regulate the transcription of genes involved in the general stress response. Functional analyses of BcAtf1 in Botrytis cinerea show that it is also connected to the SAPK BcSak1, as it shares several stress response target genes. However, Δbcatf1 mutants are not hypersensitive to osmotic or oxidative stress, as are Δbcsak1 mutants. Both BcSak1 and BcAtf1 are regulators of differentiation, but their roles in these processes are almost inverse as, in contrast with Δbcsak1, Δbcatf1 mutants are significantly impaired in conidia production and do not differentiate any sclerotia. They show extremely vigorous growth in axenic culture, with a thick layer of aerial hyphae and a marked increase in colonization efficiency on different host plants and tissues. In addition, the sensitivity to cell wall-interfering agents is increased strongly. Microarray analyses demonstrate that the loss of BcAtf1 leads to extensive transcriptional changes: apart from stress response genes, the expression of a broad set of genes, probably involved in primary metabolism, cell wall synthesis and development, is affected by BcAtf1. Unexpectedly, BcAtf1 also controls secondary metabolism: the mutant contains significantly elevated levels of phytotoxins. These data indicate that BcAtf1 controls a diversity of cellular processes and has broad regulatory functions.

Piperine inhibits aflatoxin B1 production in Aspergillus flavus by modulating fungal oxidative stress response

“…According to our results, genes belonging to bZIP-type family stand as important elements in the mechanism of action of piperine. As previously mentioned, these bZIP elements play a critical role in modulating secondary metabolite production in response to different types of stresses, thus standing as key elements in fungal adaptation to different environmental stimuli Temme et al, 2012;Van Nguyen et al, 2013;Yin et al, 2012Yin et al, , 2013. For instance, Ap-1, belonging to a redox-state sensor protein family, maintains highly conserved functions in mammalian, yeast and fungi (Toone et al, 2001).…”

Tools for Botrytis cinerea: New expression vectors make the gray mold fungus more accessible to cell biology approaches

“…As the strain is highly virulent on several host plants and yields consistently high transformation rates it has become one of the standard recipient strains in most laboratories. The genomes of B05.10 and T4 (a less aggressive isolate) were sequenced in recent years (Amselem et al, 2011) enabling detailed molecular analyses such as transcriptomic and proteomic approaches (Temme et al, 2012;Fernández-Acero et al, 2006Shah et al, 2009a,b;Espino et al, 2010). Available genome sequences and a more efficient system for construction of replacement fragments by yeast recombinational cloning such as those used by Colot et al (2006) has resulted in the rapid expansion of the number of functionally analyzed genes in B. cinerea.…”

The botrydial biosynthetic gene cluster of Botrytis cinerea displays a bipartite genomic structure and is positively regulated by the putative Zn(II)2Cys6 transcription factor BcBot6

“…It is likely that the BcSak1 pathway regulates the expression of the Bcbot genes in response to oxidative stress even though there is no evidence that the known downstream TF i.e. BcAtf1 directly acts on the BOT gene cluster (Temme et al, 2012).…”

“…The second is the stress-induced MAP kinase cascade with the downstream bZIP TF BcAtf1 (Temme et al, 2012) and the BcReg1 transcriptional regulator (Michielse et al, 2011). In addition, it was demonstrated that B. cinerea secondary metabolism is greatly influenced by light-dependent development .…”