The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non‐host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianae, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 μg/plant, whereas 50‐fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10323 and 10155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C‐terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.

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Under progressive drought stress, Brassica napus displays differential leaf modifications. The oldest leaves, developed before the onset of water deficit, wilt gradually, whereas the youngest leaves harden. Hardening was distinguished by leaf turgor and bluish wax bloom when the shoot water potential was below -3 MPa and the leaf water saturation deficit was about 60%. This adaptive change was accompanied by modifications in two-dimensional protein profiles. Ten percent of the polypeptides had altered abundance or were unique to drought-stressed plants. Two-dimensional analysis of in vitro translation products did not reveal a general decrease in mRNA population. A 22-kD double polypeptide was increased by progressive or rapid water stress and salinity and disappeared upon rehydration. These polypeptides have a common N-terminal sequence, which does not reveal homology with any known waterstress protein but which contains the signature motif of soybean Kunitz trypsin inhibitors. Immunoprecipitation allowed these polypeptides to be identified on two-dimensional gels of in vitro translation products. They appeared to be synthesized as a 24-kD precursor, and their transcript was present in the control wellwatered leaves, where the polypeptides were never detected, indicating a possible translational regulation. A putative function of this protein, named BnD22, in the retardation of drought-induced leaf senescence is discussed.Rapeseed (Brassica napus L. var oleifera) is often subjected to various environmental stresses (cold, flooding, salinity, etc.). In humid and temperate areas, drought periods are a major factor impeding plant growth and development. This species, like other Cruciferae species, displays an original adaptive strategy. When subjected to progressive drought stress, a dramatic alteration of its root system occurs, characterized by the emergence of numerous roots that remain short, hairless, and often tuberized (3). These roots are able to survive extreme soil desiccation and rapidly recover hair formation and elongation upon rehydration. A specific be-

The protein contents of mitochondria from different potato (Solanum tuberosum L.) tissues (tubers, dark-grown shoots, and green leaves) grown in a greenhouse or in vitro were compared by two-dimensional polyacrylamide gel electrophoresis. Two different methods were used: using the method that gave the highest resolution, an average number of 360 polypeptides was revealed on the mitochondrial pattems after silver staining. The mitochondrial protein patterns of etiolated tissues (tubers, darkgrown shoots) are roughly similar but distinct from those of green leaves. The four subunits of the glycine decarboxylase complex (involved in photorespiration) and a few other polypeptides are very abundant in green tissues, compared with nonphotosynthetic tissues. Conversely, some other polypeptides that are abundant in tubers and dark-grown shoots are hardly detectable in green leaf mitochondria. A rabbit antiserum was raised against a 40 kilodalton polypeptide that is among the most characteristic of these nonphotosynthetic tissue-specific polypeptides, and the Nterminal sequence of this polypeptide was determined. No effect of in vitro culture was observed on the protein composition of mitochondria isolated from differentiated tissues. However, the protein pattems of callus and cell suspension mitochondria are distinct from those of any differentiated tissues, although their basic pattem is clearly mitochondrial.