Chitinase production in pine callus ( Pinus sylvestris L.): a defense reaction against endophytes?

Abstract

In shoot tip-derived tissue cultures of Scots pine (Pinus sylvestris L.), browning and subsequent degeneration of the culture is accompanied by lipid peroxidation and lignification of cells, which are characteristic features of a plant defense reaction. Since chitinases are enzymes acting primarily in plant defense, their expression was studied in pine callus in order to elucidate the defense reaction. Chitinases were present diversely in tissue cultures originating from shoot tips and embryos of P. sylvestris, in contrast to Pinus nigra embryogenic callus, where production of chitinases or browning was not detected. Because endophytic microbes had earlier been detected in buds of Scots pine, their subsequent presence in the tissue cultures was considered a potential cause of the defense reaction. Therefore, the presence of endophytes in the tissue cultures was examined by in situ hybridization. Endophytes were found to colonize heavily in 45% of the tissue cultures of P. sylvestris and to form biofilms, while the P. nigra callus was not found to contain any microbes. The endophytes seemed to propagate uncontrollably once a tissue culture of P. sylvestris was initiated. Regardless of the high level of chitinase production in the callus, the control of the endophytes presumably becomes inadequate during the tissue culture of P. sylvestris.

Role of origin and endophyte infection in browning of bud-derived tissue cultures of Scots pine (Pinus sylvestris L.)

“…Endophytes are microbes that live inside plant tissues without causing any symptoms of disease. Endophytic bacteria and yeasts could be found in the cells of the growing callus of Scots pine whereas no endophytes were detected in the embryogenic tissue of P. nigra (Pirttilä et al 2002). Furthermore, the endophytes formed biofilms in the Scots pine calli (Pirttilä et al 2002).…”

“…Endophytic bacteria and yeasts could be found in the cells of the growing callus of Scots pine whereas no endophytes were detected in the embryogenic tissue of P. nigra (Pirttilä et al 2002). Furthermore, the endophytes formed biofilms in the Scots pine calli (Pirttilä et al 2002). In the intact Scots pine bud, the endophytes belonging to genera Methylobacterium and Pseudomonas, and the yeast Rhodotorula minuta are found in the cells of scale primordia, the meristems and around the resin ducts (Pirttilä et al 2000(Pirttilä et al , 2003.…”

“…High chitinase activities were earlier detected in the bud-derived callus cultures of Scots pine, whereas the embryogenic tissues of Pinus nigra Arn. completely lacked chitinase activity (Pirttilä et al 2002). Another difference that was observed between these tissues was the presence of endophytes.…”

Reviving of the endophytic bacterial community as a putative mechanism of plant resistance

“…In most in vitro-grown plants, the cultivable bacteria become unculturable during the first two multiplication steps (Podolich et al 2007; Thomas et al 2008). A number of endophytic species can form a biofilm inside the plant tissues (Pirttilä et al 2002;Lucero et al 2011;Podolich et al 2009), which is a trait typical for VBNC bacterial populations (Oliver 2010). The VBNC bacteria of environmental samples are generally divided into two categories, one for which appropriate laboratory conditions for growth are unknown, and another of 'persisters' (Oliver 2005).…”

The role of chitinases and glucanases in somatic embryogenesis of black pine and hybrid firs

“…Expression of many chitinases is induced by biotic [9,10] and abiotic stimuli [11]. Therefore, their function in defense mechanisms is well known and documented [12][13][14].…”