Versatile Piriformospora indica and Its Potential Applications in Horticultural Crops

Modern horticultural crop production systems target the exploitation of sustainable techniques for crop improvement while maintaining balance with the environment. Several beneficial microbes have been investigated and have yielded remarkable results. The endophytic fungus, Piriformospora indica, is one microbe group with the potential to offer numerous benefits and opportunities in modern horticultural crop production. This plant growth-promoting mycorrhizal fungus is of particular interest due to its beneficial implications in plant growth and development. The fungus has been experimentally proven to significantly improve water and nutrient/mineral absorption, early flowering, seed production/germination and plant photosynthetic capability, growth rates;especially in nutrient-deprived soils, alter the production of secondary metabolites, and promote adaptation, tolerance and/or resistance to biotic and abiotic stressors. Its unique capability to be axenically cultured makes it feasible for research and application. These attributes in combinations with its broad host range, offer immense potential for this fungus for research in horticultural plant improvement. Thus, this review highlights the potential applications of P. indica in horticultural crops research and production.

Effects of 2, 4-Dichlorophenoxy Acetic Acid andLight on Growth of Gerbera (Gerbera jamesoniicv. Daxueju) Callus

This study was conducted to determine effects of 2,4-dichlorophenoxy acetic acid(2,4-D) and light on growth of gerbera(Gerbera jamesonii cv. Daxueju) callus. Callus was induced from both petiole and leaf explants of gerbera on Murashige and Skoog medium supplemented with 3% sucrose and various concentrations of 2,4-D and placed under light and dark. Callus induction percentage, callus size and callus fresh and dry weights were efficiently higher when using petiole as explant. MS medium supplemented with 1.5 mg/L 2,4-D showed the highest callus induction percentage of 96.70%. Callus induced under light had larger weight mass. It was indicated that 1.5 mg/L 2,4-D and light could promote growth of gerbera callus from petiole explant.

Cloning and Characterization of a Tyrosine Aminotransferase( TAT)Gene in Gerbera hybrida

In our previous study,a gene predicted to encode a Tyrosine aminotransferase( TAT) was found to be significantly up-regulated in root rot diseased Gerbera by transcriptome sequencing. To confirm the genes and investigate the function,we cloned the gene by RT-PCR and then conduct bioinformatic analyses. In this study,a 1 537 bp long c DNA sequence of this gene( named as Gh TAT) was firstly cloned,which contained a coding region of 1 233 bp,which was predicted to encode a protein of 410 amino acids. Bioinformatic analysis showed that the Gh TAT was a stable hydrophobic protein without signal peptide. Subcellular location prediction result indicated that this protein located in chloroplast,which is the biosynthesis position of tyrosine and the derived products of tyrosine biosynthesis pathway. Moreover,typical Tyrosine aminotransferase domain was found in this protein,indicating that it is a TAT. According to the TAT-based phylogenetic analysis and similarity analysis,the closest relationship and highest similarity was found between Gh TAT and Halianthus annuus TAT,which again verified the TAT property of Gh TAT. Tyrosine aminotransferase( TAT) is the first enzyme in tyrosine biosynthesis pathway,whose products include many antioxidant substances such as tocopherols and tocotrienols. The up-regulation of Gh TAT in root rot diseased gerbera suggests that it may play an important role in response to the root rot pathogen infection. In addition,60 phosphorylation sites( accounting for 14. 6%) were found in this protein,suggesting that the expression of this protein and its encoding gene were greatly influenced by the phosphorylation reactions.

Characterization and functional analysis of gerbera plant defensin(PDF)genes reveal the role of GhPDF2.4 in defense against the root rot pathogen Phytophthora cryptogea

Gerbera(Gerbera hybrida),a major fresh cut flower crop,is very susceptible to root rot disease.Although plant defensins(PDFs),a major group of plant antimicrobial peptides,display broad-spectrum antifungal and antibacterial activities,PDF genes in gerbera have not been systematically characterized.Here,we identified and cloned nine PDF genes from gerbera and divided them into two classes based on phylogenetic analysis.Most Class Ⅰ GhPDF genes were highly expressed in petioles,whereas all Class Ⅱ GhPDF genes were highly expressed in roots.Phytophthora cryptogea inoculation strongly upregulated all Class II GhPDF genes in roots and upregulated all Class Ⅰ GhPDF genes in petioles.Transient overexpression of GhPDF1.5 and GhPDF2.4 inhibited P.cryptogea infection in tobacco(Nicotiana benthamiana)leaves.Transient overexpression of GhPDF2.4,but not GhPDF1.5,significantly upregulated ACO and LOX gene expression in tobacco leaves,indicating that overexpressing GhPDF2.4 activated the jasmonic acid/ethylene defense pathway and that the two types of GhPDFs have different modes of action.Prokaryotically expressed recombinant GhPDF2.4 inhibited mycelial growth and delayed the hyphal swelling of P.cryptogea,in vitro,indicating that GhPDF2.4 is a morphogenetic defensin.Moreover,the addition of GhPDF2.4 to plant culture medium alleviated the root rot symptoms of in vitro-grown gerbera seedlings and greatly reduced pathogen titer in P.cryptogea-inoculated gerbera roots in the early stages of treatment.Our study provides a basis for the use of GhPDFs,especially GhPDF2.4,for controlling root rot disease in gerbera.