Ultrastructure of Chloroplasts and Chromoplasts in Capsicum Annuum I. Thylakoid Membrane Changes During Fruit Ripening

Abstract

Developing chromoplasts in the fruit of Capsicum annuum were examined by electron microscopy. Special attention was given to changes in the thylakoid system. All grana and some intergranal thylakoids in the mature chromoplasts of the seven cultivars studied underwent lysis. The particulate nature of the granal membranes disappeared during lysis before the relationship between the partitions and locules was obscured. The changes during lysis support the globular concept of membrane structure. The selective lysis of the synaptic membranes of the granal partitions may be attributed to their distinctive composition and structure. Lipid globules (osmio‐philic) did not accumulate in the immediate region of granal lysis, indicating that they are not directly derived from membranes undergoing degradation. During and following granal lysis a profuse development of intergranal thylakoid membranes occurred in several cultivars. In some instances a thylakoid plexus (prolamellar body) was formed. This specialized structure of the thylakoid system occurs in the chromoplasts of other species as well as in other types of plastids. Extensive, concentrically arranged thylakoid sheets with specific interspaced membrane relationships were frequently associated with the plexus. Several types of membrane associations and interrelationships in the plastid are described. An analysis of one type of membrane configuration, the thylakoid sheets, indicated that one method of growth may be through intussusception into the original membrane. The development of thylakoid plexes and of extensive thylakoid sheets during or after granal lysis indicates that dynamic synthetic activities occur in the chromoplasts of some cultivars of pepper during fruit ripening.

Proteomic Analysis of Chloroplast-to-Chromoplast Transition in Tomato Reveals Metabolic Shifts Coupled with Disrupted Thylakoid Biogenesis Machinery and Elevated Energy-Production Components

“…In agreement with the structural remodeling of the internal membrane system (Spurr and Harris, 1968), this study clearly shows that the abundance of thylakoid proteins fell mostly during the transition from B to R stages while the abundance of proteins of the envelope and of the plastoglobules remained essentially unchanged and proteins of the stroma underwent a slight decrease in abundance (Fig. 7).…”

“…The events investigated include, in particular, the formation of protein-accumulating bodies and the remodeling of the internal membrane system. At the structural level, the differentiation of chromoplasts consists mainly of the lysis of the grana and thylakoids (Spurr and Harris, 1968) but also includes new synthesis of membranes derived from the inner plastid membrane and that become the site for the formation of carotenoids (Simkin et al, 2007). At the biochemical and molecular level chromoplast differentiation studies have been largely dedicated to the synthesis of carotenoids (Camara et al, 1995;Bramley, 2002).…”

Red Bell Pepper Chromoplasts Exhibit in Vitro Import Competency and Membrane Targeting of Passenger Proteins from the Thylakoidal Sec and ΔpH Pathways but Not the Chloroplast Signal Recognition Particle Pathway1

“…The chromoplasts appeared intact and uncontaminated by other organelles, as assessed by electron microscopy. They contained the typical internal membrane system that includes, using the terminology of Spurr and Harris (1968), lamellae and vesicles, which are frequently observed to be associated with the inner envelope ( Fig. 1; Spurr and Harris, 1968;Laborde and Spurr, 1973;Bouvier et al, 1994).…”

“…Heavily pigmented, photosynthetically inactive chromoplasts frequently develop from chloroplasts during ripening. This conversion involves dramatic changes in the organization and composition of the internal plastid compartment, which include the loss of proteins involved in carbon fixation in the stroma and replacement with chromoplastspecific proteins, the breakdown of the photosynthetic thylakoid membranes and loss of proteins involved in light capture and electron transfer, and, in some cases, the formation of new membranes (Spurr and Harris, 1968;Camara and Brangeon, 1981;Piechulla et al, 1987;Kuntz et al, 1989).…”

“…For example, in the fibrillar-type chromoplast of bell pepper (Capsicum annuum), the photosynthetic membranes are replaced by membranous sheets and vesicles in addition to the carotenoid-rich plastoglobules and fibrils (Spurr and Harris, 1968;Laborde and Spurr, 1973;Camara and Brangeon, 1981;Deruere et al, 1994). The often extensive internal membranes are the site of synthesis of keto-xanthophylls, which constitute the major carotenoids of red fruit (Bouvier et al, 1994).…”