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MAIN CONCLUSION: CRK28, a cysteine-rich receptor-like kinase, plays a role in root organogenesis and overall growth of plants and antagonizes abscisic acid response in seed germination and primary root growth. Receptor-like kinases (RLK) orchestrate development and adaptation to environmental changes in plants. One of the largest RLK groups comprises cysteine-rich receptor-like kinases (CRKs), for which the function of most members remains unknown. In this report, we show that the loss of function of CRK28 led to the formation of roots that are longer and more branched than the parental (Col-0) plantlets, and this correlates with an enhanced domain of the mitotic reporter CycB1:uidA in primary root meristems, whereas CRK28 overexpressing lines had the opposite phenotype, including slow root growth and reduced lateral root formation. Epidermal cell analyses revealed that crk28 mutants had reduced root hair length and increased trichome number, whereas 35S::CRK28 lines present primary roots with longer root hairs but lesser trichomes in leaves. The overall growth in soil of crk28 mutant and CRK28 overexpressing lines was reduced or enhanced, respectively, when compared to the parental (Col-0) seedlings, while germination, root growth and expression analyses of ABI3 and ABI5 further showed that CRK28 modulates ABA responses, which may be important to fine-tune plant morphogenesis. Our study unravels the participation of RLK signaling in root growth and epidermal cell differentiation.

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The osmeterium, found in papilionoid larvae, is an eversible organ with an exocrine gland that produces substances in response to the mechanical disturbances caused by natural enemies. The anatomy, histology and ultrastructure of the osmeterium, and the chemical composition of its secretion in Heraclides thoas (Lepidoptera: Papilionidae) were studied. Heraclides thoas larvae have a Y-shaped osmeterium in the thorax. The surface of the osmeterium has a rough cuticle lining cells with papillae and irregular folds, whereas the cells that limited the gland pores are irregular, folded, and devoid of papillae. Two types of cells are found: (i) cuticular epidermal cells on the surface of the tubular arms of the osmeterium and (ii) secretory cells of the ellipsoid gland within the region of the glandular pore. Cuticular epidermal cells show a thick cuticle, with several layers divided into epicuticle and lamellar endocuticle. Secretory cells are polygonal, with extensive folds in the basal plasma membrane that formed extracellular channels. The cytoplasm has mitochondria, ribosomes, and numerous vacuoles, whereas the nucleus is irregular in shape with decondensed chromatin. The chemical composition of the osmeterial secretion comprised (Z)-α-bisabolene (25.4%), α-bisabol (20.6%), ß-bisabolene (13.1%), (E)-α-bisabolene 8%), ß-pinene (9.91%), longipinene epoxide (8.92%), (Z)-ß-farnesene (6.96%), ß-caryophyllene (2.05%), farnesol (1.86%), linalyl propionate (1.86%), and 1-octyn-4-ol (1.07%). The morphological features suggest that the cuticular epidermal cells play a major role in the maintenance and protection of the osmeterium, whereas secretory cells are responsible for production of osmeterial secretions.

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BACKGROUND: The development of petal-like organs has occurred repetitively throughout angiosperm evolution. Despite homoplasy, it is possible that common underlying molecular mechanisms are repeatedly recruited to drive the development of petaloid organs. In Zingiberales, infertile, petal-like structures replace fertile stamens, resulting in petaloidy in androecial whorls. Assuming that androecial petaloidy is a shared derived characteristic, we expect to find common ultrastructure and molecular mechanisms underlying androecial petaloidy across Zingiberales. RESULTS: We show that petaloidy in Zingiberales is associated with tightly packed, protruding epidermal cells. Expression patterns for candidate genes involved in petal identity differ between the petaloid organs of Costaceae v. Cannaceae, despite similar macro- and microscopic organization. For all candidate gene families analyzed, our data suggest at least one Zingiberales-specific duplication event. CONCLUSIONS: Our data suggest that the patterns of B-class gene expression across the Zingiberales do not correlate with the occurrence of petaloidy, indicating that androecial petaloidy might have evolved independently of B-class gene expression in some lineages. It is possible that gene duplication may play a role in the diversity of petaloid structures found throughout the Zingiberales. It is likely that Zingiberales petaloidy may also result from the deployment of genes other than those involved in specification of petal identity. Developmental Dynamics 244:1121-1132, 2015. © 2015 Wiley Periodicals, Inc.