TMT-Based Quantitative Proteomic Analysis Reveals the Physiological Regulatory Networks of Embryo Dehydration Protection in Lotus (Nelumbo nucifera)

Lotus is an aquatic plant that is sensitive to water loss, but its seeds are longevous after seed embryo dehydration and maturation. The great difference between the responses of vegetative organs and seeds to dehydration is related to the special protective mechanism in embryos. In this study, tandem mass tags (TMT)-labeled proteomics and parallel reaction monitoring (PRM) technologies were used to obtain novel insights into the physiological regulatory networks during lotus seed dehydration process. Totally, 60,266 secondary spectra and 32,093 unique peptides were detected. A total of 5,477 proteins and 815 differentially expressed proteins (DEPs) were identified based on TMT data. Of these, 582 DEPs were continuously downregulated and 228 proteins were significantly up-regulated during the whole dehydration process. Bioinformatics and protein-protein interaction network analyses indicated that carbohydrate metabolism (including glycolysis/gluconeogenesis, galactose, starch and sucrose metabolism, pentose phosphate pathway, and cell wall organization), protein processing in ER, DNA repair, and antioxidative events had positive responses to lotus embryo dehydration. On the contrary, energy metabolism (metabolic pathway, photosynthesis, pyruvate metabolism, fatty acid biosynthesis) and secondary metabolism (terpenoid backbone, steroid, flavonoid biosynthesis) gradually become static status during lotus embryo water loss and maturation. Furthermore, non-enzymatic antioxidants and pentose phosphate pathway play major roles in antioxidant protection during dehydration process in lotus embryo. Abscisic acid (ABA) signaling and the accumulation of oligosaccharides, late embryogenesis abundant proteins, and heat shock proteins may be the key factors to ensure the continuous dehydration and storage tolerance of lotus seed embryo. Stress physiology detection showed that H2O2 was the main reactive oxygen species (ROS) component inducing oxidative stress damage, and glutathione and vitamin E acted as the major antioxidant to maintain the REDOX balance of lotus embryo during the dehydration process. These results provide new insights to reveal the physiological regulatory networks of the protective mechanism of embryo dehydration in lotus.

Relationship of the lateral embryo (in grasses) to other monocot embryos: a status up-grade

Martin placed the lateral embryo, which occurs only in grasses, adjacent to the broad embryo at the base of his family tree of seed phylogeny. Since Poales and Poaceae are derived monocots, we questioned the evolutionary relationship between the lateral embryo and other kinds of monocot embryos. Information was compiled on embryo and seed characteristics for the various families of monocots, kind of embryogenesis for families in Poales and germination morphology of families with lateral (only Poaceae) and broad embryos. The kinds of monocot embryos are broad, capitate, lateral, linear fully developed, linear underdeveloped and undifferentiated, but only broad and lateral embryos are restricted to Poales. Asterad embryogenesis occurs in Poaceae with a lateral embryo and in Eriocaulaceae, Rapataceae and Xyridaceae with a broad embryo. In developing grass seeds, the growing scutellum (cotyledon) pushes the coleoptile, mesocotyl and coleorhiza to the side. In the organless broad embryo, the cotyledonary sector is larger than the epicotyledonary sector. During germination of grass seeds, the coleorhiza and then the coleoptile emerge, while in a seed with a broad embryo the elongating cotyledon pushes the epicotyledonary sector outside the seed, after which a root–shoot axis is differentiated at a right angle to the cotyledon inside the seed. Broad and lateral embryos are closely related; however, the lateral embryo is more advanced in seed/embryo traits and germination morphology than the other kinds of monocot embryos, suggesting that its position on the family tree of seed phylogeny should be higher than of the other monocot embryos.

A Taxonomic Revision of the Genus Poeppigia (Fabaceae: Dialioideae)

Poeppigia is a Neotropical genus of legumes that occurs from Mexico and Cuba to eastern Brazil and is considered until now to be monospecific with two varieties. Being one of the 17 genera in the subfamily Dialioideae, Poeppigia stands out as one of the few genera with not reduced perianth and androecium, representing a possible link between this subfamily and the other Fabaceae. The genus was never revised since several taxa were described in the XIX century and lack of recent studies and proper typification. Here we revised the genus taxonomically with the analysis of more than 400 specimens and proposed the acceptance of two species: P. procera, distributed on tropical forests from Mexico to Amazon and Southeast Brazil and P. densiflora, endemic of Brazilian Caatinga. The two species are distinct for many characters as habitus, size of branch, leaf and fruits, number of leaflets, stipules and bracts and form of inflorescence. Seed, embryo, pollen and seedling descriptions, conservation assessments, illustrations, maps of distribution and an identification key are presented. Nomenclatural, biogeographical, and ecological comments and three new lectotypifications are made.

Identification of Genes and MicroRNAs Affecting Pre-harvest Sprouting in Rice (Oryza sativa L.) by Transcriptome and Small RNAome Analyses

Pre-harvest sprouting (PHS) is one of the primary problems associated with seed dormancy in rice (Oryza sativa L.). It causes yield loss and reduces grain quality under unpredictable humid conditions at the ripening stage, thus affecting the economic value of the rice crop. To resolve this issue, understanding the molecular mechanism underlying seed dormancy in rice is important. Recent studies have shown that seed dormancy is affected by a large number of genes associated with plant hormone regulation. However, understanding regarding the effect of heat stress on seed dormancy and plant hormones is limited. This study compared the transcriptome and small RNAome of the seed embryo and endosperm of two contrasting japonica rice accessions, PHS susceptible (with low seed dormancy) and PHS resistant (with high seed dormancy), at three different maturation stages. We found that 9,068 genes and 35 microRNAs (miRNAs) were differentially expressed in the embryo, whereas 360 genes were differentially expressed in the endosperm. Furthermore, we identified and verified the candidate genes associated with seed dormancy and heat stress-related responses in rice using quantitative real-time PCR. We newly discovered eight hormone-related genes, four heat shock protein-related genes, and two miRNAs potentially involved in PHS. These findings provide a strong foundation for understanding the dynamics of transcriptome and small RNAome of hormone- and heat stress-related genes, which affect PHS during seed maturation.

Degree of seed desiccation sensitivity of the Amazonian palm Oenocarpus bacaba depends on the criterion for germination

ABSTRACT Across the seed-seedling transition, several germination criteria are used in studies of palm-seed germination. In Oenocarpus bataua, these criteria have differential tolerance to thermal stress. In this study, we evaluated the tolerance of germination criteria to seed desiccation of the congeneric Oenocarpus bacaba. We dried seeds to different moisture contents (MC) before scoring first cataphyll, second cataphyll, enclosed eophyll and expanded eophyll. Seeds without drying had 41.7% MC. Germination success reached close to 70% after 75 and 105 days, depending on the germination criterion. Safe MC was close to initial MC and all seeds were dead with MC < 26.7%. As the primordial organs of the cataphylls and the eophyll are already detectable in the palm-seed embryo, all were affected by drying. Critical MC, defined here as 50% loss of germination capacity, increased from 35.4% (first cataphyll) to 37.1% (expanded eophyll) and confirmed that, across the seed-seedling transition, more advanced germination stages had a higher sensitivity to desiccation. During germination and development, the criteria appear in sequence over several weeks. Consequently, the desiccation damage was only detectable when the last criterion was evaluated. To avoid an underestimation of damages, we suggest that seed-stress studies in palms should take into account an adequate period for seedling development, which, for O. bacaba, was 105 days until the expansion of the eophyll.

Integrative Modeling of Gene Expression and Metabolic Networks of Arabidopsis Embryos for Identification of Seed Oil Causal Genes

Fatty acids in crop seeds are a major source for both vegetable oils and industrial applications. Genetic improvement of fatty acid composition and oil content is critical to meet the current and future demands of plant-based renewable seed oils. Addressing this challenge can be approached by network modeling to capture key contributors of seed metabolism and to identify underpinning genetic targets for engineering the traits associated with seed oil composition and content. Here, we present a dynamic model, using an Ordinary Differential Equations model and integrated time-course gene expression data, to describe metabolic networks during Arabidopsis thaliana seed development. Through in silico perturbation of genes, targets were predicted in seed oil traits. Validation and supporting evidence were obtained for several of these predictions using published reports in the scientific literature. Furthermore, we investigated two predicted targets using omics datasets for both gene expression and metabolites from the seed embryo, and demonstrated the applicability of this network-based model. This work highlights that integration of dynamic gene expression atlases generates informative models which can be explored to dissect metabolic pathways and lead to the identification of causal genes associated with seed oil traits.

Use of radiographic images for rapid and non-destructive assessment of crambe seed quality

Technologies based on electromagnetic radiation, such as the X-ray technique, has contributed to the establishment of new and promising methodologies for evaluating seed quality. This study aimed to relate parameters based on semi-automated analysis of radiographs of crambe seeds to their physiological quality. Radiographic images of seeds from 10 seed lots of cultivar FMS Brilhante were semi-automatically analyzed using ImageJ® software. Measurements of morphometric characteristics and tissue integrity were obtained for the seeds, as well as individually for the seed embryo. Following X-ray test, the seeds were subject to germination and seedling growth test. It was possible to visualize the internal structures of the seeds in the radiographs. There were differences in the physical parameters obtained by the semi-automated analysis of the radiographs between the seed lots. Also, the lots differed regarding the physiological quality of the seeds. Morphometric characteristics and tissue integrity, especially for the seed embryo, showed high correlation with the seed physiological quality. Therefore, this work presents an efficient approach to rapid and non-destructively assess the quality of crambe seeds.

BIOLOGY, ECOLOGY AND CONTROL OF THE PLUM SEED WASP [EURYTOMA SCHREINERI SCHREINER (HYMENOPTERA: EURYTOMIDAE)]

The plum seed wasp, Eurytoma schreineri Schr. is a new pest on plum trees in Bulgaria. It is a serious pest for plums in northeastern Bulgaria. This wasp attacks the fruits of various plum cultivars. Damage by E. schreineri on plums ranges from 26-92%. The damage percent depends upon bioecological conditions and on the susceptibility of the plum varieties. Late-flowering cultivars are the most sensitive, where the attack can reach up to 90-92% of Stanley cultivar. This is univoltine and overwinters as a fully developed larva within stones of the fallow fruit under the plum trees. During the spring, usually in early May, the adults go out of the fallen mummified fruits and after mating the females oviposit inside the newly formed plum fruit. The egg is inserted into the endosperm of the fruit before the formation of the stone. Incubation lasts about 20-22 days, and hatch begins about the time that the plum seed embryo becomes visible. Larva development is completed by the end of June or early July, then the larvae enter diapause and remain in this state for 1-3 winters. Locally penetrating insecticides, applied when the larvae begin to hatch, provide a significant degree of larval control.