Arabinogalactan-protein and pectin epitopes in relation to an extracellular matrix surface network and somatic embryogenesis and callogenesis in Trifolium nigrescens Viv

The formation of an extracellular matrix surface network (ECMSN), and associated changes in the distribution of arabinogalactan-protein and pectin epitopes, have been studied during somatic embryogenesis (SE) and callogenesis of Trifolium nigrescens Viv. Scanning electron microscopy observations revealed the occurrence of an ECMSN on the surface of cotyledonary-staged somatic embryos as well as on the peripheral, non-regenerating callus cells. The occurrence of six AGP (JIM4, JIM8, JIM13, JIM16, LM2, MAC207) and four pectin (JIM5, JIM7, LM5, LM6) epitopes was analysed during early stages of SE, in cotyledonary-staged somatic embryos and in non-embryogenic callus using monoclonal antibodies. The JIM5 low methyl-esterified homogalacturonan (HG) epitope localized to ECMSN on the callus surface but none of the epitopes studied were found to localize to ECMSN over mature somatic embryos. The LM2 AGP epitope was detected during the development of somatic embryos and was also observed in the cell walls of meristematic cells from which SE was initiated. The pectic epitopes JIM5, JIM7, LM5 and LM6 were temporally regulated during SE. The LM6 arabinan epitope, carried by side chains of rhamnogalacturonan-I (RG-I), was detected predominantly in cells of embryogenic swellings, whilst the LM5 galactan epitope of RG-I was uniformly distributed throughout the ground tissue of cotyledonary-staged embryoids but not detected at the early stages of SE. Differences in the distribution patterns of low and high methyl-esterified HG were detected: low ester HG (JIM5 epitope) was most abundant during the early steps of embryo formation and highly methyl-esterified form of HG (JIM7 epitope) became prevalent during embryoid maturation

Changes in the formation of an extracellular matrix surface network during early stages of indirect somatic embryogenesis in Drosera spathulata

Our attention was focused on the changes occurring in the cell surface network linked to the induction of embryogenic competence of pre- and pro-embryogenic stages of indirect somatic embryogenesis in the callus tissue of Drosera spathulata Labill., which originated from isolated leaves. This surface network forms as a distinct and compact layer on globular somatic embryos before formation of protoderm. Young protodermal cells had a typical furrowed surface, whilst mature protodermal cells were practically smooth. Embryogenic cells show changes in structural organisation and chemical composition of cell surface network, during different stage formation of somatic embryogenesis. Using SEM, TEM analysis and enzymatic digestion of proteins and pectins, we have shown that granular components, which represent pectic polysaccharides, were linked to induction and acquisition of embryogenic competence and pre-embryogenic stage. Fibrillar network was linked to proembryogenic stage of somatic embryogenesis. Our study has revealed that combined effect of protease and pectinase after 5 hours caused a complete disappearance and removal of the cell surface network

Cytoskeleton in the Parasitic Plant Cuscuta During Germination and Prehaustorium Formation

Although cytoskeleton is a driving force for cell division and growth in higher plants, there is little evidence about its components in parasitic angiosperms. Microtubules and actin filaments in cells of shoot apical meristem and root-like structure of stem holoparasites European (C. europaea L.) and Eastern (C. monogyna Vahl.) dodders, as well as in prehaustorium, the specific organ adapted to parasitism, were visualized for the first time by immunolabeling and fluorescence microscopy. The significance of cytoskeletal elements during germination and prehaustorium formation was addressed by treatments with taxol, oryzalin, latrunculin B, cytochalasin B/D, jasplakinolide, and 2,3-butanedione monoxime. In shoot apical meristem many dividing cells were observed, in contrast to root-like structure, devoid of cell divisions. Cortical microtubules were oriented transversely and/or obliquely, while actin filaments were randomly distributed in cells of both organs. Furthermore, longitudinal cortical microtubules were present in digitate cells of prehaustorium, and transverse arrays were found in its file cells. Long and short random actin filaments were also observed in prehaustorium cells. Thus, it was shown that the cytoskeleton in dodder shoot cells is organized in a similar way to non-parasitic dicots, while cytoskeletal organization has some peculiarities in quickly senescing root-like structure and prehaustorium

A histological and SEM study of early stages of direct somatic embryogenesis in leaves of sundew Drosera spathulata Labill.

The possibility of plant regeneration via direct somatic embryogenesis from leaf tissue of Drosera spathulata Labill. has been studied, using MS medium supplemented with various concentration of NAA and BAP. Scanning electron microscopy investigations in combination with histological analysis verified direct somatic embryogenesis by formation of globular, torpedo-shaped, heart-shaped and cotyledonary embryo like structures. Optimal somatic embryo formation occurred when leaves were pre-treated with low concentration (0.005 mg l-1) of 2,4-D within 6 h. Prolonged influence of 2,4-D to 24-48 h led to the expression of morphological and developmental abnormalities

Data_Sheet_1_Cytoskeleton in the Parasitic Plant Cuscuta During Germination and Prehaustorium Formation.docx

<p>Although cytoskeleton is a driving force for cell division and growth in higher plants, there is little evidence about its components in parasitic angiosperms. Microtubules and actin filaments in cells of shoot apical meristem and root-like structure of stem holoparasites European (C. europaea L.) and Eastern (C. monogyna Vahl.) dodders, as well as in prehaustorium, the specific organ adapted to parasitism, were visualized for the first time by immunolabeling and fluorescence microscopy. The significance of cytoskeletal elements during germination and prehaustorium formation was addressed by treatments with taxol, oryzalin, latrunculin B, cytochalasin B/D, jasplakinolide, and 2,3-butanedione monoxime. In shoot apical meristem many dividing cells were observed, in contrast to root-like structure, devoid of cell divisions. Cortical microtubules were oriented transversely and/or obliquely, while actin filaments were randomly distributed in cells of both organs. Furthermore, longitudinal cortical microtubules were present in digitate cells of prehaustorium, and transverse arrays were found in its file cells. Long and short random actin filaments were also observed in prehaustorium cells. Thus, it was shown that the cytoskeleton in dodder shoot cells is organized in a similar way to non-parasitic dicots, while cytoskeletal organization has some peculiarities in quickly senescing root-like structure and prehaustorium.</p