Redox-regulation of ion homeostasis in growing lily pollen tubes

ROS in tobacco stigma exudate affect pollen proteome and provoke membrane hyperpolarization

“…We found ROS in collected stigma exudate of tobacco, which agrees well with the previously reported fact of ROS synthesis and accumulation on stigmas of different species (McInnis et al 2006a;Zafra et al 2016), including sunflower (Sharma & Bhatla 2013), olive (Zafra et al 2010), Senecio squalidus L. and Arabidopsis thaliana (McInnis et al 2006b). ROS signaling in pollen germination has been assumed and discussed (Wudick & Feijo 2014) and putative mechanisms of ROS action on male gametophyte have been revealed in vitro (Wu et al 2010;Breygina et al 2016;Podolyan et al 2019). In particular, exogenously added H 2 O 2 caused plasma membrane hyperpolarization Podolyan et al 2019) in pollen tubes and protoplasts but the question remained whether this response appears in the presence of exudate or not.…”

“…ROS signaling in pollen germination has been assumed and discussed (Wudick & Feijo 2014) and putative mechanisms of ROS action on male gametophyte have been revealed in vitro (Wu et al 2010;Breygina et al 2016;Podolyan et al 2019). In particular, exogenously added H 2 O 2 caused plasma membrane hyperpolarization Podolyan et al 2019) in pollen tubes and protoplasts but the question remained whether this response appears in the presence of exudate or not. Here we demonstrate that hyperpolarization appears both in pollen tubes exhibiting normal MP gradient as reported earlier (Breygina et al 2010) and in pollen protoplasts treated with stigma exudate, and is abolished after catalase treatmentthus, hyperpolarization is caused by H 2 O 2 in the exudate and is a part of natural physiological crosstalk.…”

“…The sensitivity of Ca 2+ fluxes to peroxide has also been demonstrated on spheroplasts from pear pollen tubes (Wu et al 2010). In growing lily pollen tubes H 2 O 2 caused shifts of membrane potential (MP) gradient, pH gradient and [Ca 2+ ] cyt increase (Podolyan et al 2019). Thus, targets for H 2 O 2 have been found in male gametophyte, but to what extent the application of H 2 O 2 reflects the effect of exudate itself?…”

Oxygen radicals and cytoplasm zoning in growing lily pollen tubes

“…The distribution of inorganic ions is also strictly subjected to the principle of zoning, including gradient distribution of ionic currents through the plasma membrane as well as free inorganic ions in the cytoplasm (Michard et al 2017;Feijó and Wudick 2018;Zheng et al 2019). The latter is maintained due to the uneven allocation of ion transport systems and their activitywhich also results in the gradient distribution of membrane potential values, which has been to date revealed in 3 species, including lily (Breygina et al 2010;Maksimov et al 2018;Podolyan et al 2019).…”

“…Model experiments on protoplasts with exogenous ROS highlighted several aspects of pollen physiology related to redox-signaling, the main of which is ion homeostasis, as ion transport across the membrane is regulated by Н 2 О 2 Maksimov et al 2016). As Н 2 О 2 is the most stable ROS, all studies in vitro were confined to Н 2 О 2 , which was shown to have multiple effects in pollen tubes, both angiosperm (Podolyan et al 2019) and gymnosperm (Maksimov et al 2018). Studies on somatic plant cells that have been exposed to stress lead to the opinion that Н 2 О 2 doesn't affect "targets" that had been attributed to this ROS but rather binds to transition metal binding sites converting it to OH • (Demidchik 2015).…”