Ethylene promotes the abscission of leaves and the ripening of fruits in pepper plants, and in both events an increase in cellulase activity is observed. However, two enzyme isoforms (pI 7.2 and 8.5, respectively) are differentially involved in the two physiological phenomena. The pI 8.5 form has been purified from ripe fruits. It is a glycoprotein with an apparent molecular mass of 54 kDa. Two short peptides were sequenced and a very high homology to a tomato cellulase was observed. Polyclonal antibodies, raised against the purified enzyme, have allowed us to demonstrate that the observed ethylene-induced increase in cellulase activity is paralleled by de novo synthesis of protein. Three cDNAs (CX1, CX2 and CX3), encoding different cellulases, were obtained and characterized and their expression investigated. Accumulation of all three mRNAs is induced by ethylene treatment, though to different levels. CX1 is mainly expressed in ripe fruits while CX2 is especially found in abscission zones. CX3 accumulates at very low levels in activated abscission zones. Comparisons with other known cellulases demonstrate clear heterogeneity within the higher plant cellulases. Differences in ethylene inducibility and molecular structure suggest different physiological roles for cellulase in pepper plants.

Cancer‐associated fibroblasts (CAFs) are key regulators of tumorigenesis and promising targets for next‐generation therapies. We discovered that cancer cell‐derived activin A reprograms fibroblasts into pro‐tumorigenic CAFs. Mechanistically, this occurs via Smad2‐mediated transcriptional regulation of the formin mDia2, which directly promotes filopodia formation and cell migration. mDia2 also induces expression of CAF marker genes through prevention of p53 nuclear accumulation, resulting in the production of a pro‐tumorigenic matrisome and secretome. The translational relevance of this finding is reflected by activin A overexpression in tumor cells and of mDia2 in the stroma of skin cancer and other malignancies and the correlation of high activin A/mDia2 levels with poor patient survival. Blockade of this signaling axis using inhibitors of activin, activin receptors, or mDia2 suppressed cancer cell malignancy and squamous carcinogenesis in 3D organotypic cultures, ex vivo, and in vivo, providing a rationale for pharmacological inhibition of activin A‐mDia2 signaling in stratified cancer patients.

During peach (Prunus persica[L.] Batsch) fruit development and ripening the cell wall undergoes several structural and biochemical changes driven by several hydrolases. Among these, the endo‐β‐1,4‐D‐glucanase (EGase, EC 3.2.1.4), or cellulase, may play a crucial role. Involvement of EGase throughout development and ripening of the fruit of cv. Redhaven was assessed by monitoring enzyme activity, specific polypeptide accumulation and gene transcription. During the four stages of growth EGase activity was high during S1 and in the early S2, declined during S3, and increased with the onset of ripening (S4). Two isoforms with isolectric points of 6.5 and 9.5 were identified. The pI 6.5 EGase was the only form present during the early stages of growth. whereas the pI 9.5 EGase was most abundant during ripening. The same isoforms were present in leaf and fruit abscission zones. The antibody raised against the pI 9.5 EGase, purified from leaf abscission zones, cross‐reacted with a protein of 54 kDa. A cDNA clone of 753 bp encoding peach EGase was obtained by RT‐PCR. EGase transcripts, detectable only after amplification of total RNA by RT‐PCR, were observed during S1, and at the preclimacteric and climacteric stages. However, the strongest hybridisation occurred at ripening, in correspondence with the maximal enzyme activity and polypeptide accumulation, which took place before the ethylene climacteric and in the early stage of flesh softening. Propylene treatments reduced EGase activity during the early stage of fruit growth but dramatically enhanced enzyme activity and the related transcript accumulation at ripening, and accelerated the loss of firmness. In fruit treated with 2,5‐norbornadiene the softening process was strongly inhibited and the rise in EGase transcripts and activity did not take place. The results point to the EGases being involved in early fruit growth and the initial phases of softening. The presence of two isoforms and the dual effect of propylene on enzyme activity suggest that different EGase genes operate during the early and late developmental stages in peach fruit.

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Leaflet abscission in Sambucus nigra is the result of cell wall breakdown at the site of separation. Associated with wall degradation is an increase in the activity of the enzyme pl,4 giucanase (E.C.3-1.2-4) in the cells that comprise the abscission zone. The enzyme has been extracted from abscission zone tissue and purified using a substrate affinity column. A qualitative enzyme assay procedure has been developed and this has facilitated the purification process. The (31,4 giucanase enzyme has a pH optimum of 7 and a molecular mass of 54kDa. Antibodies have been raised to the purified protein. The role of the enzyme in the abscission process is discussed.