Renan Gonçalves da Silva

Climate change not only worries government representatives and organizations, but also attracts the attention of the scientific community in different contexts. In agriculture specifically, the cultivation and productivity of crops such as sugarcane, maize, and sorghum are influenced by several environmental factors. The effects of high atmospheric concentration of carbon dioxide ([CO₂]) have been the subject of research investigating the growth and development of C₄ plants. Therefore, this brief review presents some of the physiological and genetic changes in economically important C₄ plants following exposure periods of increased [CO₂] levels. In the short term, with high [CO₂], C₄ plants change photosynthetic metabolism and carbohydrate production. The photosynthetic apparatus is initially improved, and some responses, such as stomatal conductance and transpiration rate, are normally maintained throughout the exposure. Protein-encoding genes related to photosynthesis, such as the enzyme phosphoenolpyruvate carboxylase, to sucrose accumulation and to biomass growth and are differentially regulated by [CO₂] increase and can variably participate owing to the C₄ species and/or other internal and external factors interfering in plant development. Despite the consensus among some studies, mainly on physiological changes, further studies are still necessary to identify the molecular mechanisms modulated under this condition. In addition, considering future scenarios, the combined effects of high environmental and [CO₂] stresses need to be investigated so that the responses of maize, sugarcane, and sorghum are better understood.

Some metals are beneficial to plants and contribute to critical physiological processes. Some metals, however, are not. The presence of aluminum ions (Al³⁺) can be very toxic, especially in acidic soils. Considerable parts of the world’s arable land are acidic in nature; mechanistically elucidating a plant’s response to aluminum stress is critical to mitigating this stress and improving the quality of plants. To identify the genes involved in sugarcane response to aluminum stress, we generated 372 million paired-end RNA sequencing reads from the roots of CTC-2 and RB855453, which are two contrasting cultivars. Data normalization resulted in 162,161 contigs (contiguous sequences) and 97,335 genes from a de novo transcriptome assembly (trinity genes). A total of 4858 and 1307 differently expressed genes (DEGs) for treatment versus control were identified for the CTC-2 and RB855453 cultivars, respectively. The DEGs were annotated into 34 functional categories. The majority of the genes were upregulated in the CTC-2 (tolerant cultivar) and downregulated in RB855453 (sensitive cultivar). Here, we present the first root transcriptome of sugarcane under aluminum stress. The results and conclusions of this study are a crucial launch pad for future genetic and genomic studies of sugarcane. The transcriptome analysis shows that sugarcane tolerance to aluminum may be explained by an efficient detoxification mechanism combined with lateral root formation and activation of redox enzymes. We also present a hypothetical model for aluminum tolerance in the CTC-2 cultivar.

Sugarcane is an important sugar-source crop. As any other plant, it can be exposed to several abiotic stress conditions. Though some metals contribute to critical physiological processes in plants, the presence of aluminum ions (Al3+) can be very toxic. In order to develop plants that flourish in acidic soils, it is critical to gain insights into the molecular mechanisms of sugarcane response to aluminum stress. To determine the genes involved in sugarcane response to aluminum stress we generated 372 million paired-end RNA sequencing reads, from roots of CTC-2 and RB855453 two contrasting cultivars. Data normalization resulted in 162,161 contigs and 97,335 trinity genes. After the read cutoff, the differentially expressed genes were 4,858 in CTC-2 and 1,307 in the RB855453, Treatment Vs Control, respectively. The differentially expressed genes were annotated into 34 functional categories. The majority of the genes were upregulated in the CTC-2 (tolerant cultivar) and down regulated in RB855453 (sensitive cultivar). Here, we present the first root-transcriptome of sugarcane under aluminum stress. The results and conclusions of this study provide a valuable resource for future genetic and genomic studies in sugarcane. This transcriptome analysis points out that sugarcane tolerance to aluminum may be explained by an efficient detoxification mechanism combined with the lateral root formation and activation of redox enzymes. Following our results, we present here, a hypothetical model for the aluminum tolerance in CTC-2 cultivar.

This article aims was to compare two sugarcane genotypes under elevated atmospheric carbon dioxide (CO₂) concentration and soil water deficit, through an approach based on statistical analysis of plant growth multiple characteristics. For that, Pearson's correlation, dissimilarity and principal components (PC) analysis were performed, of some parameters such as stem length (culm) and roots length, number of leaves, dry mass of plant tissues, among other characteristics. Biometric attributes have a positive and significant correlation with each other. However, the dry mass values ​​have a negative correlation with the other parameters, meaning, therefore, there is a growth reduction as there is also a decrease in plants water conditions subjected to stress. Based on the dissimilarity and PC analysis, observed that genotypes genetically diverge and the imposed environmental condition influences growth responses. This preliminary study is an indication that this approach is essential for understanding the variations between the sugarcane genotypes responses. In addition, is evident (due to divergence) that analyses about the physiological and molecular responses of these genotypes in this environmental condition will contribute to the identification of regulated biological processes and possible tolerance mechanisms.

Although several metallic elements are required for plant growth, excessive amounts of aluminum ions (Al³⁺) can result in the inhibition of root growth, thus triggering water and nutrient deficiencies. Plants under stress undergo gene expression changes in specific genes or post-transcriptional gene regulators, such as miRNAs, that can lead to stress tolerance. In this study, we investigated the miRNAs involved in the response of sugarcane to aluminum stress. Four miRNA libraries were generated using sugarcane roots of one tolerant and one sensitive sugarcane cultivar grown under aluminum stress and used to identify the miRNAs involved in the sugarcane aluminum toxicity response. The contrast in field phenotypes of sugarcane cultivars in the field during aluminum stress was reflected in the micro-transcriptome expression profiles. We identified 394 differentially expressed miRNAs in both cultivars, 104 of which were tolerant cultivar-specific, 116 were sensitive cultivar-specific, and 87 of which were common among cultivars. In addition, 52% of differentially expressed miRNAs were upregulated in the tolerant cultivar while the majority of differentially expressed miRNAs in the sensitive cultivar were downregulated. Real-time quantitative polymerase chain reaction was used to validate the expression levels of differentially expressed miRNAs. We also attempted to identify target genes of miRNAs of interest. Our results show that selected differentially expressed miRNAs of aluminum-stressed sugarcane cultivars play roles in signaling, root development, and lateral root formation. These genes thus may be important for aluminum tolerance in sugarcane and could be used in breeding programs to develop tolerant cultivars.

Introdução: Himatanthus sucuuba é uma planta laticífera que pertence à família Apocynaceae, nativa da região Amazônica. É usada tradicionalmente na medicina popular como: vermífugo, tratamento de gastrite, artrite, laxativo, antianêmico, antifúngico e cicatrizante. O objetivo do trabalho foi a...