Thesis Defence: The establishment of in vitro system in Ochrosia elliptica to improve the accessibility of bioactive ellipticine

Reo Zukoshi, supervised by Dr. Thu-Thuy Dang, will defend their thesis titled “The establishment of in vitro system in Ochrosia elliptica to improve the accessibility of bioactive ellipticine” in partial fulfillment of the requirements for the degree of Master of Science in Biochemistry and Molecular Biology.

An abstract for Reo Zukoshi ‘s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.

Abstract

Ellipticine is a monoterpenoid indole alkaloid produced from Ochrosia elliptica, a plant native to northeastern Australia. Since its discovery in 1959, ellipticine has shown potent anticancer activity, along with antiviral and antimicrobial properties. However, its broader application is limited by an incomplete understanding of its biosynthetic pathway, which hinders its accessibility. Metabolite profiling of O. elliptica revealed that young roots accumulated the highest levels of ellipticine, underscoring the need for alternative production platforms. Because reports on O. elliptica in vitro cultures are scarce, this study aimed to establish callus and hairy root systems to improve access to ellipticine.

Leaf-derived calli accumulated more ellipticine than intact leaf tissues. Among the auxins tested, only naphthaleneacetic
acid (NAA)-induced calli exhibited enhanced ellipticine production. Subsequent elicitor screening identified the combination of silver nitrate (AgNO3) and methyl jasmonate (MeJA) as the most promising treatment for increasing ellipticine accumulation.

Hairy root induction was most successful with leaf explants, whereas other tissue types were compromised by endophytic fungal contamination. Among leaf explants, younger leaves showed higher transformation efficiency and produced more hairy roots, whereas hairy roots from mature leaves grew faster. Generalized linear mixed modelling indicated that although Agrobacterium rhizogenes strain AR10 achieved the highest transformation efficiency, its utility was limited by greater phytotoxicity and lower ellipticine accumulation. In contrast, strain AR1193 consistently performed well across infection methods and produced ellipticine levels comparable to those of strain ATCC15834, whose hairy roots accumulated only slightly less ellipticine than native young roots.

Therefore, AR1193 represents the most promising strain for further optimization of the hairy root system. Together, these established callus and hairy root platforms improve access to ellipticine and provide a foundation for future biosynthetic studies, metabolic engineering, and sustainable production of this medically important alkaloid in O. elliptica.