The Phaseolus suspensor and its polytene chromosomes

Plant polytene chromosomes

“…These nuclei have generally been observed in ephemeral tissues made up of only a few cells with intense metabolic activity, the main function of which is to provide nutritional support to vital organs during certain periods of development (e.g., the larval salivary glands of insects, the mammalian trophoblasts and the embryo suspensor cells of angiosperms). In such tissues, the cytoplasmatic volume and nuclei DNA content of the cells are increased by endomitosis or endoreduplication cycles (Nagl, 1974(Nagl, , 1985Nagl et al, 1985).…”

“…The underdevelopment of the cell wall of suspensor cells and their other structural characteristics indicate their secretory function in transporting nutrients through their membranes to the embryo (Nagl, 1974;Cionini, 1987). Analyses of the growth regulator level and transcription activity indicate that the suspensor tissue may play an important role during embryo ontogenesis, and seems to have a function in the synthesis of phytohormones needed for embryo development (Walbot et al, 1972;Clutter et al, 1974;Alpi et al, 1975;Cionini et al, 1976;Lorenzi et al, 1978).…”

Embryogenesis in Angiosperms: Development of the Suspensor.

“…Endopolyploidization of the nucleus often accompanies development of the suspensor (DAmato, 1984;Raghavan, 1986). The most extensive studies of polytene chromosomes in suspensors have dealt with Phaseolus (Nagl, 1974(Nagl, , 1978Tagliasacchi et al, 1983Tagliasacchi et al, , 1984Frediani et al, 1986;Forino et al, 1992). The leve1 of endopolyploidy increases toward the base of the suspensor and reaches 4000 C in /?…”

Lampbrush-type chromosomes in the primary nucleus of the green alga Acetabularia mediterranea

“…(Some authors have also described the appearance of spec ia l " puffed " regions in the polytene chromosomes of the suspensor cells of some Phaseolus species as a " lampbrush state", cf. Avanzi et al , 1970 ;Nagl, 1970Nagl, , 1973Nagl, , 1974 . In the course of our studi es on the primary (giant) nucleus of the Dasycladacean green alga Acetab' utaria, we noted the regular occurren ce of distinct chromosomal structures with a " lampbrush-like" morphology (Spring et al,j 974).…”