Optimized Regeneration of <i>Petunia</i> Protoplast and Its Association with Tissue Identity Regulators

Abstract

The popular ornamental plant Petunia is also a valuable model plant in tissue culture. Cellular conversions during differentiation and regeneration have been investigated using various combinations of phytohormones; however, studies on genes for reprogramming toward desired tissue identities have been limited. In this study, we isolated Petunia protoplasts and cultured them in the callus, rooting, or shooting stages, which were used to establish the optimal protoplast culture conditions and to identify genes that epigenetically function as tissue identifiers. The optimal conditions for plasmolysis and enzyme digestion to obtain healthy protoplasts were compared, in which combinations of Viscozyme, Celluclast, and Pectinex (VCP) enzymes were more efficient in isolating protoplasts when followed by 21 to 25% sucrose purification and washing processes. The filtered and washed protoplasts started to divide at 1 day and developed into colonies after 3 weeks of culture, which showed higher efficiency in the Murashige and Skoog (MS) salt culture media compared to that in the Kao and Michayluk (KM) salt media. The pluripotent colonies formed calli on the solid medium supplemented with 3% sucrose after 4 weeks, and were destined to the same cell mass, rooting, or shooting on the regeneration medium. Three epigenetic controllers, ATXR2, ATX4A, and ATX4B, were highly expressed in calli, shoots, and organs of shoots and roots, respectively, confirming that dedifferentiation and regeneration of tissue identity is plastic.

Keywords

• dedifferentiation
• organogenesis
• petunia
• protoplast
• regeneration