Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

Legacy Department



Luo, Hong

Committee Member

Marcotte Jr , William R

Committee Member

Schnabel , Guido

Committee Member

Chen , Chinfu


Turfgrass species are agriculturally and economically important perennial crops that are susceptible to biotic stress (e.g. fungal pathogens) and abiotic stress (e.g. salinity and drought). Every year, environmental stress significantly influences turfgrass quality and production causing economic loss globally. My research explores the feasibility of using two novel transgenes - Penaeidin4-1 (Pen4-1) from the shrimp, Litopenaeus setiferus, and microRNA319a (miR319a) from the rice, Oryza sativa, to genetically engineer turfgrass for enhanced tolerance to environmental stress.
The antimicrobial peptide - Pen4-1 has been reported to possess in vitro antifungal and antibacterial activities against various economically important pathogens. In this study, two DNA constructs were prepared containing either the coding sequence of a single peptide, Pen4-1 or the DNA sequence coding for the transit signal peptide of the secreted tobacco AP24 protein translationally fused to Pen4-1 coding sequence. Transgenic turfgrass plants containing different DNA constructs exhibited significantly enhanced resistance to dollar spot and brown patch, the two major fungal diseases in turfgrass. My results demonstrated the effectiveness of Pen4-1 in a perennial species against fungal pathogens and may suggest a potential strategy for engineering broad-spectrum fungal disease resistance in crop species.
The miR319 family is one of the first characterized miRNA families in plants and it has been demonstrated to target TEOSINTE BRANCHED/CYCLOIDEA/PCF (TCP) genes encoding plant-specific transcription factors. Transgenic plants overexpressing the rice miR319 gene, Osa-miR319a, exhibited dramatic morphological changes, including significantly decreased tiller numbers, wider and thicker leaves, larger stems, larger weight:area ratio and more total wax coverage. Overexpression of miR319 also led to enhanced drought and salt tolerance in transgenics, which might be attributed to the increased weight:area ratio and total wax coverage as well as less sodium uptake. Gene expression analysis in both wild-type and transgenic plants indicated that at least four putative miR319 target genes in turfgrass AsPCF5, AsPCF6, AsPCF8 and AsTCP14 were down-regulated in transgenic plants.
These results provide important information leading to the development of novel molecular strategies to genetically engineer crop species for enhanced performance under unfavorable environmental conditions, contributing to agriculture production.