Quantitative and qualitative study of endogenous and exogenous growth regulators in eggplant (Solanum melongena) microspore cultures

Abstract

In eggplant microspore embryogenesis, embryos are produced and then transformed into undifferentiated calli, instead of developing as true embryos. This is the main current bottleneck that precludes this process from being efficient. In this work we aimed to shed light on the factors involved in the successful in vitro development of eggplant haploid embryos by evaluating the role of growth regulators (GRs) in this process. We analyzed the endogenous levels of different GRs, including auxins, cytokinins and gibberelins, as well as salicylic, jasmonic and abscisic acid, in microspores and microspore-derived embryos at different culture stages. We also analyzed the same GR profiles in leaf and anther wall tissues of different eggplant backgrounds. Finally, we assessed the application of different GR combinations to the culture medium. Our results showed that in eggplant there are no genotype-specific endogenous GR profiles that can be associated to a high embryogenic response. Instead, the embryogenic response seems related to different GR accumulation patterns during in vitro culture. The changes observed in the endogenous levels of salicylic and abscisic acid were not related to the embryo transition. There were, however, changes in the levels of indole acetic acid and dihydrozeatin. The best GR combination to promote callus production was 0.5 mg/L 1-naphthaleneacetic acid (NAA) and 0.5 mg/L 6-benzylaminopurine (BAP). A 20% reduction of NAA and BAP reduced embryo production but produced structures more anatomically similar to embryos. These results shed light on the role of GRs during the development of microspore-derived embryos in eggplant microspore cultures.

Improving the isolated microspore culture in eggplant (Solanum melongena L.) with amino acid nutrition

“…In another study, the levels of endogenous plant growth regulators (cytokinins, auxins, gibberellins, jasmonic acid, abscisic acid, and salicylic acid) were investigated in eggplant microspore embryogenesis. Different accumulation patterns of plant growth regulators during microspore culture were linked to different embryogenic responses [ 10 ]. Even though these studies were done, the problems with the eggplant microspore embryogenesis pathway (globular embryos not changing into later embryonic stages) still exist.…”

Generating homozygous mutant populations of barley microspores by ethyl methanesulfonate treatment

“…Thousands of embryogenic calli can thus be rapidly induced, many of which can later develop into regenerated plants (Li and Devaux 2005 ; Esteves et al 2014 ). In recent years, higher frequencies of embryogenic callus formation and green plantlet regeneration have been achieved in several plant species, such as rice ( Oryza sativa ), wheat ( Triticum aestivum ), tobacco ( Nicotiana tabacum ), rapeseed, and eggplant ( Solanum melongena ) (Shariatpanahi et al 2006 ; Mohammadi et al 2012 ; Shariatpanahi and Ahmadi 2016 ; Dong et al 2021 ; Calabuig-Serna et al 2022 ; Rahman et al 2022 ). An efficient isolated microspore culture system was established in barley ( Hordeum vulgare ) following the optimization of factors that affect microspore embryogenesis (Lu et al 2008 , 2016 ).…”

Multidisciplinary study of the role of calcium in plant in vitro embryogenesis

“…In general, the inducible stage of microspore development is the transition between vacuolated microspore and young bicellular pollen . Other factors that influence microspore embryogenesis are the composition of culture medium, including macronutrients, micronutrients and phytohormones (Calabuig-Serna et al 2022;Juzoń-Sikora et al 2022), and the conditions used for in vitro culture , including the stress treatment applied to induce the embryogenic development Shariatpanahi et al 2006;Islam and Tuteja 2012). The different embryogenesis-inducing stress treatments comprehend centrifugation, changes in temperature, changes in media pH and osmotic stress among others (Asif et al 2014;Shariatpanahi et al 2006).…”

“…In rapeseed, microspore embryogenesis is induced after a heat-shock stress treatment in the absence of hormones in culture media , which indicates that, at least in some cases, the haploid or DH embryo is autonomous to suffice its own hormonal needs. However, recalcitrant species such as eggplant, pepper or cucumber require the presence of hormones in order to induce the embryogenic response (Calabuig-Serna et al 2022;Asadi and Seguí-Simarro 2021;Albiñana Palacios and Seguí-Simarro 2021;Calabuig-Serna et al 2021). Furthermore, epigenetic modifications introduced by histone deacetylases have been reported to be critical in determining the totipotency or recalcitrance of microspores.…”