The DUF642 protein family is found exclusively in spermatophytes and is represented by 10 genes in Arabidopsis and in most of the 24 plant species analyzed to date. Even though the primary structure of DUF642 proteins is highly conserved in different spermatophyte species, studies of their expression patterns in Arabidopsis have shown that the spatial-temporal expression pattern for each gene is specific and consistent with the phenotypes of the mutant plants studied so far. Additionally, the regulation of DUF642 gene expression by hormones and environmental stimuli was specific for each gene, showing both up- and down-regulation depending of the analyzed tissue and the intensity or duration of the stimuli. These expression patterns suggest that the DUF642 genes are involved throughout the development and growth of plants. In general, changes in the expression patterns of DUF642 genes can be related to changes in pectin methyl esterase activity and/or to changes in the degree of methyl-esterified homogalacturonans during plant development in different cell types. Thus, the regulation of pectin methyl esterases mediated by DUF642 genes could contribute to the regulation of the cell wall properties during plant growth.

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Seed germination is a complex process in which the embryo, enclosed within the surrounding tissues, must quickly switch from a maturation program to a germinationdriven developmental process that will prepare the embryo for seedling growth and establishment. The germination process initiates with water uptake by the dry seed and culminates, usually, with the radicle protrusion. The radicle emergence from the seed is a highly regulated process that involves discrete and coordinated changes in plant cell wall extensibility and rearrangements of its components, among other processes. In this chapter we will review current knowledge of the physiological process of controlled cell separation and expansion, which give the primary cell wall its plastic properties by "loosening" of the main components of the cell wall during seed germination. We will focus on the physiological importance of primary cell wall constitution and modification by the activity in muro of a broad variety of cell wall-modifying enzymes that include hydrolases and transglycosylases, as well as non-enzymatic processes such as expansin-mediated loosening during seed germination.

The species of the genus Ceiba produces fruits with fibers with a high content of cellulose. The fiber is used for textiles, cushion filling and for industrial purposes and its characteristics have been studied in some species including Ceiba pentandra (kapok), C. speciosa and C. aesculifolia. The use of the trunk and seeds of Ceiba has also been described for different species. This article presents a review on the biological diversity of the genus Ceiba (Malvaceae). The genus Ceiba has 18 recognized species that are distributed naturally in America and Africa. However, some Ceiba trees have been introduced to various countries, especially in Asia, due to their ornamental interest and potential uses for their fiber. Ecophysiological studies of different Ceiba species have shown that resistance to adverse environmental conditions varies from species to species. Therefore, Ceiba species are considered potentially useful in restoring ecosystems impacted by human activity. The information related to the classification, morphological characteristics, phenology, ecophysiology and distribution of the different species will be extremely relevant for the sustainable production of kapok fiber. Finally, the recent genomic and transcriptomic studies also provide a valuable resource for further genetic improvement and effective use of Ceiba trees.

Seeds constitute a key physiological stage in plants life cycle. During seed germination, there is a spatial-temporal imbibition pattern that correlates with described physiological processes. However, only the moment of testa rupture has been described as a critical, discrete stage. Could a specific relative water content (RWC) value reflect a physiological stage useful for comparisons between seed batches? We tracked seed-by-seed imbibition during germination to homogenize sampling and selected a transcriptomic approach to analyse the physiological transitions that occur in seed batches collected in different years and with contrasting phenotypic responses to a priming treatment. The seed RWC reflected the transcriptional transitions that occur during germination, regardless of imbibition time or collection year, and revealed a set of biological processes that occur in the dry seed and during early germination are associated with the phenotypic response to priming. As climate shifts, so do the timing of developmental events important for determining organismal fitness, and poses another challenge to the comprehension of molecular and physiological processes driving the interaction between organisms and environment. In this study, we demonstrate that the use of physiological traits, specific to a particular developmental stage, is a reliable time-independent approach.

Background: In crop plants, the induction of seed storage protein mobilization and synthesis of LEA family proteins has been extensively described.Question: Natural priming promotes mobilization and synthesis of seed storage and LEA proteins in wild plants?Species studied: Buddleja cordata and Opuntia tomentosa. Study site: Reserva Ecológica del Pedregal de San Angel (REPSA). Methods: Natural priming treatments were applied to B. cordata and O. tomentosa seeds during one and six months respectively. Phosphorylated proteins fractions were obtained by affinity chromatography from control and treated seeds. Differences in protein pattern between control and treated seeds were determined by electrophoresis and the treated seed proteins were identified by LS/LS/MALDITOF. Results:The phosphorylated fraction of B. cordata treated seeds presented two proteins that were absent in the control protein fraction. These two proteins were identified as two different 11S globulins. The phosphorylated fraction of O. tomentosa treated seeds also presented two proteins that were absent in the control protein fraction. These two proteins were identified as a 12S globulin and a LEA protein. Conclusion:Seeds are subjected to changes in soil water content during their permanence in soil; this natural priming process promotes mobilization and synthesis of storage and LEA proteins that are involved in stress resistance.Key words: Buddleja cordata, natural priming, Opuntia tomentosa, seed proteins. ResumenAntecedentes: La inducción de la movilización y síntesis de proteínas de reserva y de proteínas de la familia LEA en respuesta al acondicionamiento es un proceso ampliamente descrito en plantas cultivadas.Preguntas: ¿El acondicionamiento natural promueve la movilización y síntesis de las proteínas de reserva y LEA en plantas silvestres?Especies: Buddleja cordata y Opuntia tomentosa. Métodos: Se aplicó el tratamiento de acondicionamiento natural a las semillas de B. cordata y O. tomentosa durante 1 y 6 meses respectivamente. La fracción de proteínas fosforiladas se obtuvo por medio de una cromatografía de afinidad de las semillas control y tratadas. Las diferencias en el patrón proteico entre semillas control y tratadas se determinaron por medio de una electroforesis y las proteínas de las semillas tratadas fueron identificadas por LS/LS/MALDITOF. Resultados:En las semillas tratadas de B. cordata se detectaron dos proteínas identificadas como 11S globulinas y en las semillas tratadas de O. tomentosa se detectaron dos proteínas correspondientes a una 12S globulina y una proteína LEA. Conclusiones:Durante su estancia en el suelo, las semillas están sujetas a cambios en el contenido de agua del suelo y este proceso de acondicionamiento natural promueve la movilización y síntesis de proteínas de reserva y LEA en las semillas, involucradas en la resistencia a estrés.Palabras clave: Acondicionamiento natural, Buddleja cordata, Opuntia tomentosa, proteínas de la semilla. Botanical Sciences (1): 76-83, 2018This is an open access article ...

Plant cell wall remodeling is an important process during plant responses to heat stress. Pectins, a group of cell wall polysaccharides with a great diversity of complex chemical structures, are also involved in heat stress responses. Enzymatic activity of the pectin methyl esterases, which remove methyl groups from pectins in the cell wall, is regulated by DUF642 proteins, as described in different plants, including Arabidopsis thaliana and Oryza sativa. Our results demonstrated that heat stress altered the expression of the DUF642 gene, BIIDXI. There was an important decrease in BIIDXI expression during the first hour of HS, followed by an increase at 24 h. bdx-1 seedlings had less tolerance to heat stress but presented a normal heat stress response; HSFA2 and HSP22 expressions were highly increased, as they were in WT seedlings. Thermopriming triggered changes in pectin methyl esterase activity in WT seedlings, while no increases in PME activity were detected in bdx-1 seedlings at the same conditions. Taken together, our results suggest that BIIDXI is involved in thermotolerance via PME activation.

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