Maturation of somatic embryos in two embryogenic cultures of Picea morrisonicola Hayata as affected by alternation of endogenous IAA content

Abstract

Embryogenic culture lines T4 and T2 were initiated from two mature zygotic embryos of Picea morrisonicola Hay. Mature somatic embryos (SEs) were produced in culture line T2 but not in line T4 after 8-week abscisic acid (ABA) treatment. High performance liquid chromatography (HPLC) analysis of the endogenous indole-3-acetic acid (IAA) content has shown 7.5 times higher IAA production in T4 line than in T2 line during the proliferation phase. However, after ABA incubation the line T4 produced much less IAA than line T2. The application of an anti-auxin, 2,3,5-triiodobenzoic acid (TIBA) or 2-(4-chlorophenoxy)-2-methylpropionic acid (PCIB) induced culture line T4 to produce mature SEs. Both 1 lM TIBA and 5 lM PCIB increased the production of stage 2 SEs in T4 culture line when cultures were treated during the proliferation stage for 8 weeks. Occasionally cotyledonary (stage 3) SEs were even produced from treated T4 culture line. Both chemicals have also been demonstrated to significantly decrease the amount of IAA in the treated T4 and T2 embryogenic lines. However the decrease of the IAA level was not beneficial for SE production in the T2 embryogenic line. These results indicated the importance of endogenous IAA level in manipulating the process of SE maturation in spruce embryogenic cultures.

The role of auxins in somatic embryogenesis of Abies alba

“…The effect of lower concentrations was less dramatic but a stimulating effect of PCIB on the development of somatic embryos was not found in the concentration range used. Our results are contrary to those of Find et al [46] and Liao et al [44] who obtained an increase in the yield and quality of somatic embryos of Abies nordmanniana and Picea morrisonicola by exogenous treatments with several auxin antagonists, including PCIB. They suggested that the effects of endogenously produced auxin may be one reason for low or failing maturation of embryogenic cultures.…”

“…PCIB was also used successfully to inhibit auxin action in the ESM of fir [46] and was found to retard proliferation and promote the development of numerous high-quality mature embryos of Abies nordmanniana [46]. PCIB used in Picea morrisonicola proliferation increased embryo production in embryogenic culture with high auxin production [44]. The effect of PCIB on the maturation of Abies alba ESM in this study is strongly dependent on the concentration used.…”

“…It is very difficult to counterbalance the auxin treatment during proliferation with the same treatment during maturation. Early events in embryogenesis are crucial for the successful development of somatic embryos [44,47]. The same effect has been described in the process of embryogenesis of other plants such as Lycopersicum [48].…”

“…In contrast, our results show no inhibitory effect of auxin on proliferation of early somatic embryos of Abies alba but do indicate a negative effect of auxin during maturation. We can therefore only speculate about the optimal timing of auxin or antiauxin treatment during somatic embryogenesis [44].…”

Effects of explant, media and growth regulators on in vitro regeneration and antioxidant activity of Juniperus phoenicea

“…The anti-auxin transport inhibitor TIBA and the growth retardant DM have been utilized in plant tissue culture to adjust the endogenous hormonal balance of in vitro cultured explants, in order to induce a specific differentiation in tissues (Lall et al, 2005;Liao et al, 2008;Kepenek and Karoğlu, 2011). This was supported in the current study by the formation of adventitious shoots and roots in response to TIBA and DM but not cytokinins.…”