Rhizoid Differentiation in Spirogyra

Abstract

Localization of phytochrome which mediates rhizoid differentiation in Spirogyra was investigated. The red-absorbing form of phytochrome (Pr) seems to be distributed all over the cel periphery which remained in the centripetal end part after the centrifugation, as rhizoids formed equally well with red spotlight irradiation of three different parts of an end cell, i.e. distal end, middle, and proximal end, and with irradiation of centrifugal and centripetal end parts of a centrifuged end cell. The Pr distribution was confirmed with an experiment using far red irradiation over the entire cell, centrifugation, and red spotlight irradiation. The Pr-phytochrome molecules appeared to be mobile because no dichroic orientation was shown with polarized red spotlight irradiation. On the contrary, it is suggested that far red-absorbing form of phytochrome molecules are evacuated from the centripetal end part by the centrifugation in an experiment involving red irradiation over the entire ceUl-centrifugation-far red spot irradiation. Rhizoid formation was repressed markedly by far red irradiation of the centrifugal end part but not of the centripetal end part.The mode of function of the phytochrome in a physiological response, or a molecular description of the receptor/effector chain for a stimulus-response system remains unknown in spite of much work in this area. Reports on the distribution of phytochrome, especially within the plant cell, and on particle-or membranebound phytochrome are increasing, thus reflecting the importance of these subjects as clues toward understanding the mode of function.Four methods are applicable to determine the localization of phytochrome: (a) a method using microspectrophotometer; (b) a physiological method based on the effect of local irradiation of R' or FR in vivo (3); (c) a biochemical method using cell fractionation by density (1, 4, 6, 9-13); (d) an immunocytochemical method (5). The first method cannot be used for a cell containing Chl. The third and the fourth methods involve the risk of intervention by phytochromes not involved in the physiological reaction or nonactive ones. Thus, the second method seemed the best for determining the location of the phytochrome which mediated a physiological reaction.Some species of the green alga, Spirogyra, grow in small streams attached to the beds by rhizoids. The rhizoids appear 3 to 8 hr after light irradiation mostly at the tips of end cells of the filaments (7,8). Rhizoid cell differentiation is controlled by phytochrome as shown by the fact that the differentiation is induced by brief Study of phytochrome in a system free of the complications of intercellular interactions should be valuable. The Spirogyra seems to be such a system since effect of light irradiation is restricted within the right cell irradiated as shown below, ie. the effect can be detected in the cell. We applied the second physiological method of giving spotlight to determine the intracellular localization of phytochrome, together with a method utilizing centrifug...

Characteristics of softwater streams in Rhode Island II. Composition and seasonal dynamics of macroalgal communities

“…However, some species may also be high temperature-intolerant, as noted by Whitton (1975) . Alternatively, photoperiod regulation may be important in the timing of the development for some taxa, such as Spirogyra, Batrachospermum and Lernanea (Nagata, 1979 ;Huth, 1979Huth, & 1981 .…”

Arabinogalactan Proteins and the Extracellular Matrix of Charophytes: A Sticky Business

“…When wounded, Spirogyra produces rhizoids for attachment to substrates. Rhizoid formation in Spirogyra has been studied in the past and has been shown to require distinct environmental cues and reactive signaling mechanisms (Nagata, 1979; Inoue et al, 2002; Kim et al, 2005; Ikegaya et al, 2008). In this alga, the production of a cellular structure (rhizoid) with a large surface area (branched) and coated with a highly adherent-CAM that contains AGP would be critical for rapid attachment to a substrate upon wounding.…”