Camila Pegoraro

Genomic evolution and complexity of the Anaphase-promoting Complex (APC) in land plants

BackgroundThe orderly progression through mitosis is regulated by the Anaphase-Promoting Complex (APC), a large multiprotein E3 ubiquitin ligase that targets key cell-cycle regulators for destruction by the 26 S proteasome. The APC is composed of at least 11 subunits and associates with additional regulatory activators during mitosis and interphase cycles. Despite extensive research on APC and activator functions in the cell cycle, only a few components have been functionally characterized in plants.ResultsHere, we describe an in-depth search for APC subunits and activator genes in the Arabidopsis, rice and poplar genomes. Also, searches in other genomes that are not completely sequenced were performed. Phylogenetic analyses indicate that some APC subunits and activator genes have experienced gene duplication events in plants, in contrast to animals. Expression patterns of paralog subunits and activators in rice could indicate that this duplication, rather than complete redundancy, could reflect initial specialization steps. The absence of subunit APC7 from the genome of some green algae species and as well as from early metazoan lineages, could mean that APC7 is not required for APC function in unicellular organisms and it may be a result of duplication of another tetratricopeptide (TPR) subunit. Analyses of TPR evolution suggest that duplications of subunits started from the central domains.ConclusionsThe increased complexity of the APC gene structure, tied to the diversification of expression paths, suggests that land plants developed sophisticated mechanisms of APC regulation to cope with the sedentary life style and its associated environmental exposures.

Importance of heat shock proteins in maize

Abiotic and biotic stress conditions cause extensive losses to maize production, mainly due to protein dysfunction in these conditions. In higher plants, the occurrence of heat-shock proteins (HSPs) in response to different environmental stresses is a universal phenomenon and has been well documented. Many studies have demonstrated that most HSPs are involved in many regulatory pathways, act as molecular chaperones for other cell proteins, and have strong cytoprotective effects. Although many functional roles for HSPs are known, the mechanisms for these multiple functions are not entirely understood. Here we reviewed the correlation among HSP genes/proteins and plant tolerance, especially maize, in different environmental stresses. Due to the low availability of information regarding the expression of HSP genes in response to different stresses in maize, we decided to mine databases in order to generate new insights related to this topic.

Ethylene response factors gene regulation and expression profiles under different stresses in rice

Stresses can cause large yield reductions in cultivated plants. The response to these stresses occurs via a plethora of signalling pathways, where a large number of genes is induced or repressed. Among the environmental stress responsive genes, there are the members of the ethylene response factors (ERF) gene family. The mRNA levels of different ERF are regulated by many hormones and molecules produced under different stress conditions. In this study, with the goal of identifying the response of rice ERF genes to environmental stress, it was analysed the transcriptional expression profile of 114 of these genes under stress by anoxia, salt and Magnaporthe grisea. Also, aiming to characterize how the regulation of ERF genes occurs, the amount of known cis regulatory elements in the promoter region of these genes and their association with the expression profiles under the tested conditions were also assessed. The results indicate that some ERF members present the same specific expression profiles under different environmental stresses, while others do not. Within the ERF family, the regulation of gene expression is complex for some genes which have many cis elements in their promoters, but simple for others, demonstrating high levels of divergence among them. The findings demonstrate the importance of the study of each ERF separately, since it is not possible to establish general rules for regulation and probably for the function of these genes.

Effects of pre-harvest gibberellic acid spraying on gene transcript accumulation during peach fruit development

In order to understand early molecular events associated with increase in fruit size and woolliness prevention induced by pre-harvest gibberellic acid (GA3) spraying, differential transcript accumulation of genes encoding proteins putatively involved in protein folding and protection, cell wall metabolism, and endomembrane transport was studied during fruit development of ‘Chiripá’ peach. Woolliness occurrence reached 100% in untreated peach, was reduced by 15% with GA3 spraying at the end of the pit hardening stage and was significantly reduced (by 78%) in peaches treated at the beginning of the pit hardening stage despite a significantly increased fruit size. Low incidence of woolliness after cold storage and fruit size increase in early GA3 treated peach was correlated with high transcript accumulation of genes encoding proteins putatively involved in protein folding, and protection of the endoplasmic reticulum (heat shock proteins—HSP40 er) and chloroplast (HSP17.8 ch), endomembrane transport (GTPase), as well as genes involved in cell wall loosening (expansins—Exp1, Exp2, Exp3, Exp4).

Evolutionary analysis of the SUB1 locus across the Oryza genomes

BackgroundTolerance to complete submergence is recognized in a limited number of Asian rice (Oryza sativa L.) varieties, most of which contain submergence-inducible SUB1A on the polygenic SUBMERGENCE-1 (SUB1) locus. It has been shown that the SUB1 locus encodes two Ethylene-Responsive Factor (ERF) genes, SUB1B and SUB1C, in all O. sativa varieties. These genes were also found in O rufipogon and O nivara, wild relatives of O. sativa. However, detailed analysis of the polygenic locus in other Oryza species has not yet been made.FindingsChromosomal location, phylogenetic, and gene structure analyses have revealed that the SUB1 locus is conserved in the long arm of chromosome 9 in most Oryza species. We also show that the SUB1A-like gene of O. nivara is on chromosome 1 and that Leersia perrieri, a grass-tolerant to deep-flooding, presents three ERF genes in the SUB1 locus.ConclusionWe provide here a deeper insight into the evolutionary origin and variation of the SUB1 locus and raise the possibility that an association of these genes with flooding tolerance in L. perrieri may exist.

Effects of hypoxia storage on gene transcript accumulation during tomato fruit ripening

Tomato (Solanum lycopersicum L.) is a climacteric fruit, i.e., during ripening an increase in ethylene synthesis and high rate of respiration are observed. Low oxygen levels might inhibit or block ethylene biosynthesis and therefore retard the ripening process. Despite commercial applications of low oxygen treatments, the precise mode of action of low oxygen in fruit tissues and ripening is not well understood. In order to delineate the molecular responses to low oxygen stress in fruits, hypoxia-responsive tomato genes encoding heat shock factors, heat shock proteins, and enzymes involved in fermentation and ethylene synthesis pathways were analyzed. In this study, tomato fruit stored under hypoxia conditions showed that HSP17.7 and HSP21 genes were highly induced by low oxygen level, indicating their primary role in maintaining cellular homeostasis after this stress.

Efeito da radiação ultravioleta-C no controle de Monilinia fructicola

A radiação UV-C vem sendo utilizada como método alternativo no controle de doenças na pós-colheita de frutos. A podridão parda é uma das principais doenças que acomete pêssegos desde o início do desenvolvimento até a senescência. Neste trabalho, avaliou-se o efeito da radiação UV-C na indução de resistência à podridão parda de pêssegos cv. Chimarrita, em frutos com e sem ferimentos. As variáveis avaliadas foram a severidade da doença, o teor de compostos fenólicos e a capacidade antioxidante. A aplicação da radiação UV-C, tanto como controle preventivo como curativo, não protegeu o pêssego contra a infecção do patógeno, mesmo em frutos sem ferimento. Entretanto, atrasou em um dia o aparecimento de lesões nos frutos não feridos, o que pode ser interessante economicamente para a cadeia produtiva do pêssego. Ao avaliar o teor de compostos fenólicos totais e a capacidade antioxidante, verificou-se que frutos submetidos à radiação UV-C tiveram incrementos nessas propriedades. Tal fato indica que esse tratamento físico (UV-C) estimula o metabolismo secundário, ao menos da síntese de compostos fenólicos, mas não é suficiente para gerar resistência à podridão.

Rice genotypes for drought tolerance: morphological and transcriptional evaluation of auxin-related genes

Drought stress affects crop quality and productivity. The challenge of increasing food availability for a growing worldwide demand relies on the development of tolerant cultivars that will need to be adapted to arid and semi-arid areas. In order to help the understanding of rice response to stress, the phenotypic response of 6 Brazilian rice cultivars and 2 different crosses between them were characterized under drought conditions. Since gene regulation is an important part of root morphological responses to stressful conditions, 4 genes related to auxin response and root modifications (OsGNOM1 CRL4, OsIAA1, OsCAND1 and OsRAA1) were evaluated. The expression of these genes was analyzed in stressed rice using public available microarray data and then through real-time quantitative polymerase chain reaction (RT-qPCR), in the 6 phenotypically evaluated Brazilian genotypes under standard conditions (absence of stress). Our results show that all genotypes lengthened its roots in response to drought, specially the 2 hybrids. The expression of these genes is modified in response to stress, and OsRAA1 has a very special behavior, constituting a target for future studies. Further steps include the study of polymorphisms in these genotypes in order to understand if differences in these genes or in regulatory regions can be associated with differences in root system architecture and/or stress tolerance.

Efeito de danos mecânicos, da redução de temperatura e 1-MCP no metabolismo pós-colheita de brócolis Legacy

O etileno acelera o metabolismo pos-colheita de brocolis, e sua sintese e induzida por danos mecânicos e pelo aumento da temperatura. Para testar esta hipotese, foram realizados 03 experimentos. No primeiro, avaliou-se o efeito do dano mecânico na producao do etileno; no segundo, estudou-se o efeito do armazenamento refrigerado; e, no terceiro, o efeito do 1-MCP no metabolismo e conservacao de brocolis. Os resultados mostraram que o dano mecânico aumenta significativamente a producao do etileno, passando de 0,25 a 501,83 mL.h-1 g-1, duas horas apos a aplicacao do tratamento. Ja, no tratamento controle, os incrementos foram menores, passando de 0,27 para 203,13 mL.h-1 g-1. Durante o armazenamento, observou-se que a deterioracao ocorreu mais rapidamente no tratamento controle (20-22 °C), com intenso amarelecimento, degradacao de clorofilas e formacao de odor desagradavel. Os brocolis armazenados a 0-2 e a 5-7 °C mantiveram boa qualidade por 12 dias. A aplicacao de 1-MCP nao contribuiu para prolongar a vida-de-prateleira de brocolis Legacy a 20-22 °C, nao tendo havido efeito na preservacao da coloracao esverdeada, nem na prevencao da degradacao de clorofilas.

Oryza glumaepatula Steud.

Oryza glumaepatula is the only native wild rice from the Americas that has a diploid genome (2n = 24). Thus, this species constitutes a source of genetic variability for the improvement of Oryza sativa cultivated in the New World. Wild rice species are important sources of commercially important characters, such as tolerance to acid soils and drought, yield potential, cytoplasmic male-sterility, heat tolerance, and elongation ability. The transference of alleles associated to target characters from O. glumaepatula into O. sativa could be done via introgression or through the use of genetic engineering. Oryza glumaepatula occurs in Central and South America and Caribe, growing in flooded areas, swamps, rivers, and humid areas with clay soils and that present invasive or colonizing behavior. It presents populations with perennial, annual, or biannual cycle, depending of geographical localization, with bushy growth, fragile stems near the base of plants, which can detach and fluctuate, forming new populations. Flowering occurs between October and November, presenting self- and outcrossing. Recently, O. glumaepatula had its genome sequenced, enabling comparative studies among different Oryza species. These studies suggest the expansion and contraction of gene families, diversity, and variation in the number of noncoding genes and divergence in the sequences among the species are associated with the adaptation of each species to different environmental conditions. These results demonstrate the importance of species from the Oryza genus in the development of new O. sativa cultivars.