Androgenesis-inducing stress treatments change phytohormone levels in anthers of three legume species (Fabaceae)

Legumes are recalcitrant to androgenesis and induction protocols were only recently developed for pea (Pisum sativum L.) and chickpea (Cicer arietinum L.), albeit with low regeneration frequencies. Androgenesis is thought to be mediated through abscisic acid (ABA) but other phytohormones, such as auxins, cytokinins, and gibberellins, have also been implicated. In view of improving induction protocols, the hormone content of pea, chickpea, and lentil anthers was measured after exposure to cold, centrifugation, electroporation, sonication, osmotic shock, or various combinations thereof using an analytical mass spectrometer. Indole-3-acetic acid (IAA) had a key function during the induction process. In pea, high concentrations of IAA-asparagine (IAA-Asp), a putative IAA metabolite, accumulated during the application of the different stresses. In chickpea, the IAA-Asp concentration increased 30-fold compared to pea but only during the osmotic shock treatment and likely as a result of the presence of exogenous IAA in the medium. In contrast, no treatment in lentil (Lens culinaris) invoked such an increase in IAA-Asp content. Of the various cytokinins monitored, only cis zeatin riboside increased after centrifugation and electroporation in pea and possibly chickpea. No bioactive gibberellins were detected in any species investigated, indicating that this hormone group is likely not linked to androgenesis in legumes. In contrast to the other stresses, osmotic shock treatment caused a reduction in the levels of all hormones analyzed, with the exception of IAA-Asp in chickpea. A short period of low hormone content might be a necessary transition phase for androgenesis induction of legumes. Key message Five androgenesis-inducing stress treatments changed content of ABA, auxin and cytokinin in anthers of three legumes. Osmotic shock treatment differed because it reduced hormone content to very low levels.