Nucellus Epidermis Research Articles

Ectopic expression of TAPETUM DETERMINANT1 affects ovule development in Arabidopsis.

Plants have evolved to extensively employ leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest family of RLKs, to control growth, development, and defense. In Arabidopsis thaliana, the EXCESS MICROSPOROCYTES1 (EMS1) LRR-RLK and its potential small protein ligand TAPETUM DETERMINANT1 (TPD1) are specifically required for anther cell differentiation; however, TPD1 and EMS1 orthologs also control megaspore mother cell proliferation in rice and maize ovules. Here, the molecular function of TPD1 was demonstrated during ovule development in Arabidopsis using a gain-of-function approach. In ovules, the EMS1 gene was primarily expressed in nucellus epidermis and chalaza, whereas the expression of TPD1 was weakly restricted to the distal end of integuments. Ectopic expression of TPD1 caused pleiotropic defects in ovule and seed development. RNA sequencing analysis showed that ectopic expression of TPD1 altered expression of auxin signaling genes and core cell-cycle genes during ovule development. Moreover, ectopic expression of TPD1 not only affected auxin response but also enhanced expression of cyclin genes CYCD3;3 and CYCA2;3 in ovules. Thus, these results provide insight into the molecular mechanism by which TPD1-EMS1 signaling controls plant development possibly via regulation of auxin signaling and cell-cycle genes.

Ovule and seed structure in <i>Scolopia zeyheri</i> (Scolopieae), with notes on the embryology of Salicaceae

Scolopia zeyheri (Nees) Harv. is a widespread African tree and a member of the largest genus of the tropical Old World tribe Scolopieae (Salicaceae sensu lato). This light microscopic study is the first report on ovule and seed structure in the genus and the tribe. Ovules vary from four to six per ovary, are anatropous. crassinucellate. bitegmic and occur in an epitropous (rarely pleurotropous). median-parietal position in the unilocular, usually bicarpellate ovary. A very extensive nucellus cap. comprising nucellus epidermal derivatives and parietal tissue, characterizes the young ovule during mega- sporogenesis and megagametogenesis, but the chalazal nucellus is poorly developed. During meiosis. the micropvlar dyad cell degenerates early. The functional dyad cell forms two megaspores of which the chalazal one usually develops into a Polygonum-type embryo sac. At maturity, the micropylar end of the embryo sac is covered by the remnants of the nucellus epidermis, the parietal tissue having degenerated. The globular embryo has a short suspensor and lies in nuclear endosperm becoming cellular. The seed coat develops from both integuments, is tannimferous. has a glabrous surface with stomata and a single layer of exotegmic, longitudinal fibres.Results are compared with relevant information previously reported for genera in the tribes Flacourtieae. Samvdeae. Saliceae, Scyphostegiae and for Oncoha Forssk. (Salicaceae sensu lato). Embryologically Scolopia shows a number of ple- siomorphic features compared to other Salicaceae. For example, it lacks an extranucellar embryo sac. an apomorphic fea­ture in many Salicaceae. A summary of ovule and seed characters in Salicaceae sensu lato is given and contrasted with data available for Achariaceae sensu lato. Embryological data broadly supports the reclassification of genera, traditionally referred to Flacourtiaceae. amongst Salicaceae sensu lato and Achariaceae sensu lato.

Histochemical Investigation on the Accumulation of Phosphorus and Lipid in Aleurone Cell of Rice Kernels

The histochemical investigations on localization and properties of inorganic phosphorus, organic phosphorus and lipid were carried out mainly in aleurone layer of rice kernels. The results obtained are fummarized as follows. 1. Three to four days after flowering, inorganic phosphorus was found distributed markedly in dorsal conductive tissues, nucellar epidermis and inner integument. 2. From 5th to 11th days, the differentiation of the aleurone cells became distinct and at the same time the reaction of inorganic phosphorus and organic phosphorus were conspicuous in these cells. On the other hand the reactions became less distinct in epidermis of nucellus and inner integument. From 15th day, phytin phosphate was markedly accumulated in rice brain. At the time of the differentiation of the aleurone grains, the amounts of inorganic phosphorus and organic phosphorus in these grains became the most abundart in all tissues of rice kernel. 3. Organic and inorganic phosphorus were found to be localized in almost the same conductive tissues, but they were present only in small amounts in starch cells. 4. From these results, it is assumed that the inorganic phosphorus and sugar phosphorus, transported into rice kernels from leaves and stems, are translocated via the same conductive tissues. At the first stage, both imported phosphorus stay in the conductive tisses. At the second stage, with the differentiation of aleurone cell and, at the last stage, with the differentiation of aleurone grains, the imported inorganic phosphorus was accumulated in these organs respectively. The sugar phosphorus, at the 2nd and 3rd stages, seems to be transported to starch cells, after the permeation through aleurone cells. Then inorganic phosphorus, liberated in the starch syhthesis, seems to be accumulated in aleurone cells or aleurone grains, via phosphorus body. Phytic acid shosphorus seemes to be synthesized from the inorganic phosphorus in these organs. 5. Three days after flowering, lipids appeared as droplets and were developed in aleurone cell. Lipips were distributed much in outer space of aleurone grains but also found to be contained in these grains.

Histochemical Studies on Accumulating Process of Fat and Aleurone Grains in Rice Kerne

This is an histochemical study of fat and aleurone grains in rice kernel during ripening Processes. The results obtained are summarized as follows: 1) It was observed that the aleurone layer and embryo was rich in fat by staining with Sudan black B and Sudan III. Epidermis of nucellus also showed black coloration with Sudan black B as its cell wall thickened. 2) Fat accumulation in aleurone layer began at the 7th day, and was completed at the 15th day after flowering respectively. 3) Aleurone gsains were clearly observed by ether treatment for removal of fat in cross section of rice kernel. 4) Aleurone grain of rice kernel was a globle, about 2μin diameter and simpld with no structure in it. 5) This aleurone grain was stained by fuchsin basic and carmine acetate, but not by safranine, methylen blue, methyle orange, eosin, neutral red and iodine potassium iodine 6) Protein reaction of aleurone grain by ninhydrin, Millon's reagent and mercuric chloride BPB was not observed. 7) This grain is soluble in 0.1 N-HC1, but insoluble in 0, 1 N-NaOH. In view of the fact that 0, 1N-HC1 is the reagent of extraction of phytine in cereal grain, aleusone grain of rice kernel seems to be rich in phytine. 8) It was late ripening period (the 20th day after flowering) that aleurone grain was clearly noticed in aleurone layer of rice kernel.

Development of the Seed of Asparagus officinalis

In a study2 having to do with methods of hastening the germination of common asparagus seeds, it became necessary to determine the stages in the development of certain seed structures. This investigation was later extended, and the results are here presented. The seed of common asparagus arises from an anatropous ovule, two ovules normally being borne in each of the three locules of the ovary. The seed coat is black, finely rugose, and somewhat brittle. The embryo is a slender, threadlike structure completely imbedded in the hard, horny endosperm, the walls of which are hemicellulose. The structure of the mature seed of asparagus is briefly described and figured by HARZ. His descriptions and figures, however, show certain errors, which undoubtedly were due to his failure to follow through the changes which the seed structures undergo in their development. For example, he regards the structureless membrane just beneath the seed coat as the epidermis of nucellus, whereas developmental studies show this to be of integumentary origin. Both paraffin sections and sections of fresh seeds were employed. The latter were found to be particularly helpful. All drawings were made with a camera lucida. Integument At the time of pollination, the inner integument of the ovule consists of two cell layers, and the outer integument of from five to ten layers (figs. I-3) . The line of demarcation between the integuments I Contribution from the Division of Botany, College of Agriculture, University of California. 2 BORTHWICK, H. A., Factors influencing the rate of germination of the seed of Asparagus officinalis. Calif. Agric. Exp. Sta., Tech. Paper i8. I925. 3 HARZ, C. D., Landwirtschaftliche Samenkunde. i885. 4 In all the figures of this paper the following indicators are used: de, disintegrating endosperm cells; e, endosperm; em, embryo; gr, stem growing point; I, hilum; ii, inner integument; m, micropyle; n, nucellus; oi, outer integument; pe, pitted, thick walled endosperm; pm, pectic membrane; r, root tip; rc, root cap; s, seed coat; sac, embryo sac; sm, suberized membrane; su, suspensor; te, thin walled endosperm cells. Botanical Gazette, vol. 8o] [426