Induction of Somatic Embryogenesis in Tamarillo (Solanum betaceum Cav.) Involves Increases in the Endogenous Auxin Indole-3-Acetic Acid

Abstract

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 callus (NEC). In this work the endogenous levels of auxin along the induction phase and in the calli samples were investigated using chemical quantifications by colorimetric reactions and HPLC as well as immunohistochemistry approaches. Differential gene expression (IAA 11, IAA 14, IAA 17, TIR 1, and AFB3) 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 calli, 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.

The improvement of the in vitro plant regeneration in barley with the epigenetic modifier of histone acetylation, trichostatin A

“…Similarly, callus cultures of other in vitro recalcitrant barley cultivars (“Haruna Nijo” and “Morex”) accumulated IAA at a level different from the GP culture (Hisano et al 2016 ). Although the links between auxin content in explants/callus and the plant regeneration potential were also reported in other plant species (Nic-Can and Loyola-Vargas 2016 ), in vitro responding genotypes indicated both higher and lower accumulation of IAA than those in vitro recalcitrant (Żur et al 2015 ; Hisano et al 2016 ; Grzyb et al 2017 ; Caeiro et al 2022 ).…”

Genome-Wide Identification and Expression Analysis of the Aux/IAA Gene Family of the Drumstick Tree (Moringa oleifera Lam.) Reveals Regulatory Effects on Shoot Regeneration

“…In contrast, the expression of MoIAA13 (lamu_GLEAN_10011219) increased with increasing treatment time ( Figure 7 ). IAA11 and IAA14 gene expression exhibits a general downward trend throughout the embryogenic callus induction process in Tamarillo, while IAA17 expression appears greater than that in the initial explant [ 41 ]. Other research has revealed that shoot regeneration ability was hampered by increased IAA12 expression [ 21 ].…”

Integrated transcriptomic and metabolic analyses provide insights into the maintenance of embryogenic potential and the biosynthesis of phenolic acids and flavonoids involving transcription factors in Larix kaempferi (Lamb.) Carr.

“…In this study, IAA was found to be highly accumulated in EC ( Supplementary Table 3 ), which may be attributed to the higher expression level of one YUC gene (Lk07754) and one TAA1 gene (Lk22753) in EC. IAA participation in maintenance of multiplying cells has been demonstrated in SE of rubber tree ( Hevea brasiliensis ), and the higher accumulation of IAA in EC compared to NEC have been reported in Douglas-fir ( Pseudotsuga menziesii ) and Tamarillo ( Solanum betaceum ) ( Gautier et al., 2019 ; Caeiro et al., 2022 ). Additionally, it has been reported that the increase in endogenous auxin biosynthesis play a role in determining developmental cell fate and in activating the proliferative activity of proembryo cells ( Pérez-Pérez et al., 2019 ).…”