Gibberellin and auxin production by plant root-fungi and their biosynthesis under salinity-calcium interaction

Abstract

Rhizosphere and rhizoplane of fababean (Vicia faba), melochia (Corchorus olitorius), sesame (Sesamum indicum) and soyabean (Glycine max) plants are inhabited with fungi, mostly Aspergillus flavus, A. niger, Fusarium oxysporum, Penicillium corylophilum, P. cyclopium, P. funiculosum and Rhizopus stolonifer. All fungal species have the ability to produce gibberellin (GA) but F. oxysporum was found to produce both GA and indole-acetic acid (IAA). The optimum period for GA and IAA production by F. oxysporum was 10 days in the mycelium and 15 days in the filtrate at 28°C. The contents of GA and IAA were significantly increased at 0.5 and 1% NaCl after 5 days, but they were lowered at 4% (700 mM) NaCl. Cytochrome P-450 was significantly increased under salt stress at 0.5-7% NaCl. Calcium decreased NaCl stress on F. oxysporum by significant elevating GA biosynthesis at 40 mM Ca 2+ /700 mM Na + . GA at 10 µM and Ca 2+ at 10 mM enhanced the germination of seeds under 175 mM Na + .Keywords: GA; IAA; cytochrome; fungi; calcium; salinityThe microbial synthesis of plant growth regulators (gibberellin and auxin) is an important factor in soil fertility (Kampert and Strzelczyk 1975). Gibberellin (GA) and indole-acetic acid (IAA) are secondary metabolites, which are important biotechnological products, produced commercially from fungi for the agricultural and horticultural industry (Deacon 1984, Bruckner 1992. GA was isolated from Gibberella fujikuroi by T. Yabuta and IAA was isolated from Rhizopus suinus by K.V. Thimann in 1935. GA 3 is the dominant component of the gibberellin complexes isolated from fungi (Bozhkova et al. 1991). It is now generally agreed that GA and IAA are very widely distributed throughout the plant kingdom.Salinity represents one of the most important factors exerting stress on fungal as well as plant cell metabolism. Kaur et al. (1998) found that GA 3 at 6µM concentration induced increased germination and seedling growth under salt stress. Calcium is particularly important nutrient in plants exposed to NaCl stress because of its role in maintaining the structural and functional integrity of membrane (Leopold and Willing 1984) and in cell wall extensibility (Taiz 1984).No recent study explains the ability of filamentous fungi, associated with roots of plant crops, for the GA and IAA production and their role toward the host plant crops. Also, no studies explain the effect of salinity on the activity of rhizosphere and rhizoplane fungi and role of Ca 2+ and GA in alleviation the salt stress. The present work was commenced by collecting four plant crops for isolation of both rhizosphere and rhizoplane fungi, and screening their efficiencies for GA and IAA production. Also, effect of salinity on GA, IAA and cytochrome P-450 biosynthesis by F. oxysporum was studied. The roles of GA and Ca 2+ in reversing the toxicity of salt stress effect in seedlings were also studied. MATERIAL AND METHODSCollection of samples. Ten samples of fababean (Vicia faba), melochia (Corchorus olitorius), sesame (Sesamum ind...

EndophyticCephalotheca sulfureaAGH07 reprograms soybean to higher growth

“…The PDA slants were used for storage purpose. Czapek broth medium, containing 1% glucose and peptone was used for GA production (Hasan 2002) by incubating the fungal isolates at 308C at 120 rpm for 7 days. The wild type strain of G. fujikuroi was used as a positive control for GAs production during this experiment.…”

PERAN MIKROBA ENDOFITIK PADA BIJI KARET (Hevea Brasiliensis) TERHADAP PERKECAMBAHAN DAN PERTUMBUHAN AWAL TANAMAN

“…Kemampuan Trichoder ma sp. dalam menginduksi pertumbuhan kecambah biji kakao telah dilaporkan oleh Bailey et al (2011). Hasan (2002 melaporkan bahwa bagaimana Aspergillus sp.…”

“…Secara umum giberelin dibutuhkan dalam mengaktifkan proses perkecambahan biji (Waqas et al, 2012;Taiz & Zeiger, 2002) menyebutkan beberapa jamur endofitik mampu menghasilkan Ga1, Ga3, Ga4 dan Ga7 yang dapat meningkat biomassa tanaman inangnya. Pemberian giberelin e k s o g e n o u s b a h k a n m e n i n g k a t k a n perkecambahan biji pada kondisi cekaman Natrium (Hasan, 2002). Auksin berperan dalam aktivitas meristem pucuk dan memicu perkembangan tunas-tunas apikal ataupun tunas lateral (Taiz & Zeiger, 2002).…”

Efficiency of indoleacetic acid, gibberellic acid and ethylene synthesized in vitro by Fusarium culmorum strains with different effects on cereal growth

“…The capacity for auxin and ethylene synthesis is common among microorganisms, while gibberellin synthesis is restricted to a small group of fungal and bacterial strains (Chaqué et al 2002;Hasan 2002;Hedden & Thomas 2012). Microbial phytohormones are secondary metabolites, which are "non-essential" to life, but are involved in competition, defence and dispersal (Betina 1995;Fox & Howlett 2008).…”

“…The most typical properties of GA (a diterpenoid plant hormone) include the enhancement of stem growth, control of seed germination and plant flowering, parthenocarpic development of fruit, senescence, breaking of winter dormancy and stimulation of synthesis of hydrolytic enzymes in germinating cereal grain (Tudzynski 1999;Tsavkelova et al 2008;Yamaguchi 2008). The capacity for GA synthesis is common among pathogenic and non-pathogenic fungal and bacterial genera associated with plants and/or soil, such as Fusarium, Aspergillus, Penicillium and Rhizopus (MacMillan 1999(MacMillan , 2002Hasan 2002;Kawaide 2006;Khan et al 2008). Ethylene has a "triple effect" on plant growth and development phenomena, namely, it reduces root and shoot elongation, changes the direction of shoot growth to horizontal, and causes swelling of the hypocotyl (increased shoot thickness) (Glick et al 1998;Akhtar et al 2005;Glick 2005).…”