Spatio-Temporal Distribution of Cell Wall Components in the Placentas, Ovules and Female Gametophytes of Utricularia during Pollination.

Bartosz Jan Płachno,Anna Bogucka-Kocka,Krzysztof Banaś,Piotr Świątek,Vitor F O Miranda,Małgorzata Kapusta

doi:10.3390/ijms22115622

Abstract

In most angiosperms, the female gametophyte is hidden in the mother tissues and the pollen tube enters the ovule via a micropylar canal. The mother tissues play an essential role in the pollen tube guidance. However, in Utricularia, the female gametophyte surpasses the entire micropylar canal and extends beyond the limit of the integument. The female gametophyte then invades the placenta and a part of the central cell has direct contact with the ovary chamber. To date, information about the role of the placenta and integument in pollen tube guidance in Utricularia, which have extra-ovular female gametophytes, has been lacking. The aim of this study was to evaluate the role of the placenta, central cell and integument in pollen tube pollen tube guidance in Utricularia nelumbifolia Gardner and Utricularia humboldtii R.H. Schomb. by studying the production of arabinogalactan proteins. It was also determined whether the production of the arabinogalactan proteins is dependent on pollination in Utricularia. In both of the examined species, arabinogalactan proteins (AGPs) were observed in the placenta (epidermis and nutritive tissue), ovule (integument, chalaza), and female gametophyte of both pollinated and unpollinated flowers, which means that the production of AGPs is independent of pollination; however, the production of some AGPs was lower after fertilization. There were some differences in the production of AGPs between the examined species. The occurrence of AGPs in the placental epidermis and nutritive tissue suggests that they function as an obturator. The production of some AGPs in the ovular tissues (nucellus, integument) was independent of the presence of a mature embryo sac.

Highlights

This article is an open access articleIn typical angiosperm plants, the female gametophyte is hidden in the ovule and is covered by the nucellus and one or two integuments [1]
In Utricularia nelumbifolia and U. humboldtii, there was an intense accumulation of arabinogalactan proteins (AGPs) in the embryo sac, especially in the micropylar enlarged part of the central cell (Figure 2D–H)
Nelumbifolia and U. humboldtii, there was an intense accumulation of AGPs

Summary

Introduction

The female gametophyte (embryo sac) is hidden in the ovule and is covered by the nucellus and one or two integuments [1]. Sporophytic tissues protect the female gametophyte and transport nutrients to it, and guide the male gametophyte to the female gametophyte e.g., [3,4,5,6,7]. The great success of angiosperms is associated with the diverse structure of their styles and ovules and the sites of the pollen tube pathway [8,9,10,11]. There is a dialogue between the male gametophytes and sporophytic tissues [12], but there is competition between the pollen tubes, i.e., gametophytic competition [9,13].

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