2024-03-29T15:19:42Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/2214592021-12-28T16:52:10Zcom_10261_131com_10261_2col_10261_384
00925njm 22002777a 4500
dc
MacCabe, Andrew P.
author
Ninou, E.I.
author
Pardo, Ester
author
Orejas, Margarita
author
2020-10-02
l-rhamnose (6-deoxy-mannose) occurs in nature mainly as a component of certain plant structural polysaccharides and bioactive metabolites but has also been found in some microorganisms and animals. The release of l-rhamnose from these substrates is catalysed by extracellular enzymes including α-l-rhamnosidases, the production of which is induced in its presence. The free sugar enters cells via specific uptake systems where it can be metabolized. Of two l-rhamnose catabolic pathways currently known in microorganisms a non-phosphorylated pathway has been identified in fungi and some bacteria but little is known of the regulatory mechanisms governing it in fungi. In this study two genes (lraA and lraB) are predicted to be involved in the catabolism of l-rhamnose, along with lraC, in the filamentous fungus Aspergillus nidulans. Transcription of all three is co-regulated with that of the genes encoding α-l-rhamnosidases, i.e. induction mediated by the l-rhamnose-responsive transcription factor RhaR and repression of induction in the presence of glucose via a CreA-independent mechanism. The participation of lraA/AN4186 (encoding l-rhamnose dehydrogenase) in l-rhamnose catabolism was revealed by the phenotypes of knock-out mutants and their complemented strains. lraA deletion negatively affects both growth on l-rhamnose and the synthesis of α-l-rhamnosidases, indicating not only the indispensability of this pathway for l-rhamnose utilization but also that a metabolite derived from this sugar is the true physiological inducer.
Microbial Cell Factories 19(1): 188 (2020)
http://hdl.handle.net/10261/221459
10.1186/s12934-020-01443-9
1475-2859
http://dx.doi.org/10.13039/501100003329
http://dx.doi.org/10.13039/501100000780
33008411
Aspergillus nidulans
L-rhamnose catabolism
Transcriptional regulation
RhaR
CCR
CreA-independent
LRA
lraA/AN4186
l-rhamnose dehydrogenase
RT-qPCR
α-l-rhamnosidases
Catabolism of l-rhamnose in A. nidulans proceeds via the non-phosphorylated pathway and is glucose repressed by a CreA-independent mechanism