Jekyll encodes a novel protein involved in the sexual reproduction of barley. Plant Cell

Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
The Plant Cell (Impact Factor: 9.34). 08/2006; 18(7):1652-66. DOI: 10.1105/tpc.106.041335
Source: PubMed


Cereal seed development depends on the intimate interaction of filial and maternal tissues, ensuring nourishment of the new generation. The gene jekyll, which was identified in barley (Hordeum vulgare), is preferentially expressed in the nurse tissues. JEKYLL shares partial similarity with the scorpion Cn4 toxin and is toxic when ectopically expressed in Escherichia coli and tobacco (Nicotiana tabacum). In barley, jekyll is upregulated in cells destined for autolysis. The gene generates a gradient of expression in the nucellar projection, which mediates the maternal-filial interaction during seed filling. Downregulation of jekyll by the RNA interference technique in barley decelerates autolysis and cell differentiation within the nurse tissues. Flower development and seed filling are thereby extended, and the nucellar projection no longer functions as the main transport route for assimilates. A slowing down in the proliferation of endosperm nuclei and a severely impaired ability to accumulate starch in the endosperm leads to the formation of irregular and small-sized seeds at maturity. Overall, JEKYLL plays a decisive role in the differentiation of the nucellar projection and drives the programmed cell death necessary for its proper function. We further suggest that cell autolysis during the differentiation of the nucellar projection allows the optimal provision of basic nutrients for biosynthesis in endosperm and embryo.

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Available from: Volodymyr Radchuk
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    • "The increase in the level of this protein has been associated with structural changes in the nucellar projections, so that a gradient is generated from the crease region to the autolysing cells close to the endosperm cavity. Repression of the gene encoding JEKILL impairs the differentiation of the nucellar projections, which affects the exchange of nutrients between the pericarp and the endosperm (Radchuk et al., 2006). The gradient observed in the nucellar projections, from the crease region to the endosperm cavity, has also been observed by large-scale in situ hybridization expression analyses (Drea et al., 2005) and by laser micro-dissection pressure catapulting-based transcriptome analyses (Thiel et al., 2008). "
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    ABSTRACT: The life cycle of cereal seeds can be divided into two phases, development and germination, separated by a quiescent period. Seed development and germination require the growth and differentiation of new tissues, but also the ordered disappearance of cells, which takes place by a process of programmed cell death (PCD). For this reason, cereal seeds have become excellent model systems for the study of developmental PCD in plants. At early stages of seed development, maternal tissues such as the nucellus, the pericarp, and the nucellar projections undergo a progressive degeneration by PCD, which allows the remobilization of their cellular contents for nourishing new filial tissues such as the embryo and the endosperm. At a later stage, during seed maturation, the endosperm undergoes PCD, but these cells remain intact in the mature grain and their contents will not be remobilized until germination. Thus, the only tissues that remain alive when seed development is completed are the embryo axis, the scutellum and the aleurone layer. In germinating seeds, both the scutellum and the aleurone layer play essential roles in producing the hydrolytic enzymes for the mobilization of the storage compounds of the starchy endosperm, which serve to support early seedling growth. Once this function is completed, scutellum and aleurone cells undergo PCD; their contents being used to support the growth of the germinated embryo. PCD occurs with tightly controlled spatial-temporal patterns allowing coordinated fluxes of nutrients between the different seed tissues. In this review, we will summarize the current knowledge of the tissues undergoing PCD in developing and germinating cereal seeds, focussing on the biochemical features of the process. The effect of hormones and redox regulation on PCD control will be discussed.
    Full-text · Article · Jul 2014 · Frontiers in Plant Science
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    • "Transfer depends on the particular morphology of the NP. Hence, regular differentiation of the NP is required for proper growth and development of the endosperm (Radchuk et al., 2006; Wang et al., 1995; Cochrane, 1983). Moreover, the invention of a NP in Triticeae is probably important for evolution of large and round grains (Hands et al., 2012). "
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    ABSTRACT: In cereal grains, the maternal nucellar projection (NP) constitutes the link to the filial organs, forming a transfer path for assimilates and signals towards the endosperm. At transition to the storage phase, the NP of barley (Hordeum vulgare) undergoes dynamic and regulated differentiation forming a characteristic pattern of proliferating, elongating, and disintegrating cells. Immunolocalization revealed that abscisic acid (ABA) is abundant in early non-elongated but not in differentiated NP cells. In the maternally affected shrunken-endosperm mutant seg8, NP cells did not elongate and ABA remained abundant. The amounts of the bioactive forms of gibberellins (GAs) as well as their biosynthetic precursors were strongly and transiently increased in wild-type caryopses during the transition and early storage phases. In seg8, this increase was delayed and less pronounced together with deregulated gene expression of specific ABA and GA biosynthetic genes. We concluded that differentiation of the barley NP is driven by a distinct and specific shift from lower to higher GA:ABA ratios and that the spatial–temporal change of GA:ABA balances is required to form the differentiation gradient, which is a prerequisite for ordered transfer processes through the NP. Deregulated ABA:GA balances in seg8 impair the differentiation of the NP and potentially compromise transfer of signals and assimilates, resulting in aberrant endosperm growth. These results highlight the impact of hormonal balances on the proper release of assimilates from maternal to filial organs and provide new insights into maternal effects on endosperm differentiation and growth of barley grains.
    Full-text · Article · Jul 2014 · Journal of Experimental Botany
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    • "The regulatory mechanism of the PCD in the maternal tissue is still unclear. In barley, an analysis of the genes that are specifically expressed in the maternal tissues revealed that an aspartic protease-like protein is specifically expressed in the nucellus during nucellus degradation (Chen and Foolad, 1997), and JE- KYLL is involved in the degradation process of the nucellar projection (Radchuk, 2006). In addition, the g-VPE–type Cys proteases and a Ser protease are highly expressed in the nucellus (Sreenivasulu et al., 2006). "
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    ABSTRACT: The MADS box transcription factors are critical regulators of rice (Oryza sativa) reproductive development. Here, we here report the functional characterization of a rice MADS box family member, MADS29, which is preferentially expressed in the nucellus and the nucellar projection. Suppressed expression of MADS29 resulted in abnormal seed development; the seeds were shrunken, displayed a low grain-filling rate and suppressed starch biosynthesis, and contained abnormal starch granules. Detailed analysis indicated that the abnormal seed development is due to defective programmed cell death (PCD) of the nucellus and nucellar projection, which was confirmed by a TUNEL assay and transcriptome analysis. Further studies showed that expression of MADS29 is induced by auxin and MADS29 protein binds directly to the putative promoter regions of genes that encode a Cys protease and nucleotide binding site-Leu-rich repeat proteins, thereby stimulating the PCD. This study identifies MADS29 as a key regulator of early rice seed development by regulating the PCD of maternal tissues. It provides informative clues to elucidate the regulatory mechanism of maternal tissue degradation after fertilization and to facilitate the studies of endosperm development and seed filling.
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