Bicarbonate gradients modulate growth and colony morphology inAspergillus nidulans

Abstract

Fungal colonies expand through apically extending peripheral hyphae. These long and relatively unbranched leaders leave behind cells that show a higher degree of branching and lower growth rates. Towards the centre of the colony, quiescent, but viable cells sustain processes such as transport of water, solutes and organelles, and support the concerted genesis of specialized reproductive structures. A survey of chemical signals controlling changes in hyphal growth and branching of Aspergillus nidulans in solid minimal medium revealed that progressive accumulation of bicarbonate from the periphery to the centre of the colony effected a dual modulation of both parameters. At areas immediately behind the periphery, bicarbonate induced progressive branching without a significant change in the specific growth rate. At distal and central regions, increased branching was accompanied by progressive inhibition of the specific growth rate. The results provide new evidence that chemical cues participate in the control of colony morphology and function, which are likely to vary with changing environmental conditions.

The synthetic strigolactone GR24 influences the growth pattern of phytopathogenic fungi

“…In fact, branching in some non-mycorrhizal fungi was often found to be related to stress (Ghosh 2006;Munoz et al 2006;Yulianti et al 2006;Jha and Anjaiah 2007;Asante et al 2008;Islam 2008;Graz et al 2009;Rodriguez-Urra et al 2009;Kozlova et al 2010). In this case, branching of AM fungi may also have originated as a stress response, as mentioned above, but during the co-evolution of these fungi with SL secreting plants this stress response has secondarily further developed to produce a hyphal architecture that promotes the chances for AM fungi to encounter a plant host.…”

Boron Tolerance in Aspergillus nidulans Is Sustained by the SltA Pathway Through the SLC-Family Transporters SbtA and SbtB

“…Interestingly, SbtA, SbtB and Bor1p present high similarity to Arabidopsis thaliana BOR1 and animal bicarbonate transporters (such as NaBC1, an eletrogenic Na+-coupled borate transporter also involved in boron homeostasis) [ 35 , 36 ]. Bicarbonate has been found to modulate colonial growth in A. nidulans [ 37 ]. However, single or double null sbtA and stbB strains do not exhibit colonial growth defects that could be associated to intracellular toxic levels of bicarbonate or the accumulation of bicarbonate salts in the medium.…”

Adaptative and Developmental Responses to Stress in Aspergillus nidulans

“…Synthesis of endogenous bicarbonate induces progressive branching without a significant change in the specific growth rate at areas immediately behind the periphery of surface cultures [183]. At distal and central regions, increased branching was accompanied by progressive inhibition of the specific growth rate.…”