Distributive Patterns Of Lectin Receptors On The Membrane Surface Of Sexual Cells In Relation To Fertilization In Angiosperm

The interaction between lectins and their specific receptors is believed to play a critical role during fertilization in animals and some lower plants. However, for higher plants there is almost no information on lectins or their receptors related to male and female gametes and fertilization. Therefore, fluorescein isothiocyanate (FITC) conjugated lectins, namely concanavalin agglutinin (Con A), wheat germ agglutinin (WGA) and soybean agglutinin (SBA), were used to localize lectin receptors on plasma membrane of male and female gametes and other relevant sexual cells, as well as embryos of various developmental stages of Nicotiana tabacum and Torenia fournieri by cooled charge coupled device (CCD) and Confocal Laser Scanning Microscope (CLSM). Main results are described as follows:1. As the first attempt, it was designed to reveal the general pattern of lectin receptor distribution on the surface of female cells, namely egg cells, central cells and synergids of Torenia fournieri and, especially, toensure the possible effects of cell isolation procedure on the distribution of lectin receptors by four different systems. Con A and WGA receptors on the surface of both in vitro and in situ living female cells were localized by FITC conjugated Con A and WGA as probes. We demonstrated that enzymatic treatment and isolation procedure did not notably modify the surface characteristic of the female cells and the distributional patterns of Con A and WGA receptors. It was also found that Con A receptors were distributed differently on the surface of the female cells, with the strongest fluorescent signal on central cells and the weakest on egg cells. Calcium could greatly enhance the binding of Con A to cell surface. A polar distribution pattern of Con A receptors in embryo sacs was observed. The receptors were obviously densest at the filiform apparatus of the synergids. The basic pattern of WGA receptor distribution was similar to that of Con A's. However, the fluorescent signal of WGA was much weaker than that of Con A. Fluorescent patches of FITC-WGA were usually found on the cells surface.2. FITC conjugated Con A and WGA were used as probes to localize their receptors on the surface of unfertilized and fertilized female cells of tobacco. Polar distribution of Con A receptors was observed on the plasma membrane of unfertilized egg cells and central cells. But after fertilization, Con A receptors were distributed uniformly on the surface of female cells. Relation between localization of nucleus and polar distribution of Con A receptors on surface of central cell and egg cell was also studied. Results indicated that Con A receptors were usually denser on membrane surface near nucleus than other part of central cells, while in egg cells it was contrary to that of central cell. Factors influencing distribution of Con A receptors were also investigated. WGA receptors were also present on plasma membrane of central cell, egg cell and synergid. But after fertilization, no WGA receptors weredetected on plasma membrane of zygote and primary endosperm cell. Clearly, fertilization induced redistribution of lectin receptors on female cell surface.3. FITC-lectins were used to localize their specific receptors on the plasma membrane of generative cells (GCs) isolated from Vicia faba Lind., Iris tectorium Maxim, and Hippeastrum vittatum Herb.. The investigation on possible distributive dynamic of lectin receptors during developmental process from generative cells to sperm cells was performed. All the three lectin receptors were found on the surface of generative cells of V. faba and /. tectorium. However, on generative cells of H. vittatum only Con A and WGA receptors were observed. The same lectin receptors on the generative cells from different species showed various distributive patterns. The distribution of various lectin receptors on the same generative cells also showed different characteristics; Lectin receptors were totally absent on some generative cells of all three investigated species;...