Characterization of novel mutants with an altered gibberellin spectrum in comparison to different wild-type strains of Fusarium fujikuroi

Abstract

The rice pathogen Fusarium fujikuroi is known for producing a wide range of secondary metabolites such as pigments, mycotoxins, and a group of phytohormones, the gibberellic acids (GAs). Bioactive forms of these diterpenes are responsible for hyperelongation of rice stems, yellowish chlorotic leaves, and reduced grain formation during the bakanae disease leading to severely decreased crop yields. GAs are also successfully applied in agriculture and horticulture as plant growth regulators to enhance crop yields, fruit size, and to induce earlier flowering. In this study, six F. fujikuroi wild-type and mutant strains differing in GA yields and the spectrum of produced GAs were cultivated in high-quality lab fermenters for optimal temperature and pH control and compared regarding their growth, GA production, and GA gene expression levels. Comparative analysis of the six strains revealed that strain 6314/ΔDES/ΔPPT1, holding mutations in two GA biosynthetic genes and an additional deletion of the 4'-phosphopantetheinyl transferase gene PPT1, exhibits the highest total GA amount. Expression studies of two GA biosynthesis genes, CPS/KS and DES, showed a constantly high expression level for both genes under production conditions (nitrogen limitation) in all strains. By cultivating these genetically engineered mutant strains, we were able to produce not only mixtures of different bioactive GAs (GA3, GA4, and GA7) but also pure GA4 or GA7. In addition, we show that the GA yields are not only determined by different production rates, but also by different decomposition rates of the end products GA3, GA4, and GA7 explaining the varying GA levels of genetically almost identical mutant strains.

Endophytes Aspergillus caespitosus LK12 and Phoma sp. LK13 of Moringa peregrina produce gibberellins and improve rice plant growth

“…The presence of GA 4 in CF of both endophytes shows the subsequent conversion of GA 14 and GA 4 on desaturation then yields GA 3 and GA 7 . While GA 1 production is different from them, which is the minor product of 13-hydroxylation of GA 4 and does not convert into GA 3 (Albermann et al 2013;Waqas et al 2014). GC/MS SIM is an established method to identify targeted novel secondary metabolites (Supplementary information 1) and the absence of the GA in the fungal-free culture broth supported our results.…”

“…During the bioassay, the rice seeds were fully grown on agar water media till the harvest in order to accurately measure the sole effect of fungal CF (Khan et al 2011a(Khan et al , 2011b. Fusarium fujikuroi produces a wide array of diterpenoids including a group of phytohormones mainly GAs (Albermann et al 2013). We compared the effect of CF of wild-type F. fujikuroi with that of our endophytes and found a similar growth-promoting behavior (Hamayun et al 2010;Khan et al 2011aKhan et al , 2011bKhan et al , 2013.…”

Endophytic Paecilomyces formosus LHL10 Augments Glycine max L. Adaptation to Ni-Contamination through Affecting Endogenous Phytohormones and Oxidative Stress

“…The presence of aforementioned genes involved in the GAs biosynthesis pathway validated the GA producing capability of endophytic P. formosus LHL10. Previously, same GA gene cluster has also been reported in Fusarium fujikuroi , Gibberella fujikuroi , and Fusarium proliferatum (Tudzynski et al, 2001; Albermann et al, 2013; Rim et al, 2013). However, there is no information on GA gene biosynthetic pathway in Paecilomyces sp.…”

Gibberellins and the Red Pigments Bikaverin and Fusarubin

“…However, recently it was shown that overexpression of hmgR and fppS resulted in a reduced production level, probably due to a negative feedback regulation of HmgR. Subsequent deletion of the transmembrane domains of HmgR, which are known to be responsible for negative feedback regulation by intermediates of sterol biosynthesis, and overexpression of the remaining catalytic domain led to a 2.5-fold increased GA content [ 109 ].…”