Induction of Somatic Embryogenesis in Tamarillo (<i>Solanum betaceum</i> Cav.) Involves Increases in the Endogenous Auxin Indole-3-Acetic Acid
2022
André Caeiro | Sandra Caeiro | Sandra Correia | Jorge Canhoto
Somatic embryogenesis (SE) is a complex biological process regulated by several factors, such as the action of plant growth regulators, namely auxins, of which the most physiologically relevant is indole-3-acetic acid (IAA). In tamarillo, an optimized system for induction of SE creates, after an induction process, embryogenic (EC) and non-embryogenic <i>callus</i> (NEC). In this work the endogenous levels of auxin along the induction phase and in the <i>calli</i> samples were investigated using chemical quantifications by colorimetric reactions and HPLC as well as immunohistochemistry approaches. Differential gene expression <i>(IAA 11, IAA 14, IAA 17, TIR 1,</i> and <i>AFB3</i>) analysis during the induction phase was also carried out. The results showed that the endogenous IAA content is considerably higher in embryogenic than in non-embryogenic <i>calli</i>, with a tendency to increase as the dedifferentiation of the original explant (leaf segments) evolves. Furthermore, the degradation rates of IAA seem to be related to these levels, as non-embryogenic tissue presents a higher degradation rate. The immunohistochemical results support the quantifications made, with higher observable labeling on embryogenic tissue that tends to increase along the induction phase. Differential gene expression also suggests a distinct molecular response between EC and NEC.
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