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Anther development is a complex process essential for plant reproduction and crop yields. In recent years, significant progress has been made in the identification and characterization of the bHLH transcription factor family involved in anther regulation in rice and Arabidopsis, two extensively studied model plants. Research on bHLH transcription factors has unveiled their crucial function in controlling tapetum development, pollen wall formation, and other anther-specific processes. By exploring deeper into regulatory mechanisms governing anther development and bHLH transcription factors, we can gain important insights into plant reproduction, thereby accelerating crop yield improvement and the development of new plant breeding strategies. This review provides an overview of the current knowledge on anther development in rice and Arabidopsis, emphasizing the critical roles played by bHLH transcription factors in this process. Recent advances in gene expression analysis and functional studies are highlighted, as they have significantly enhanced our understanding of the regulatory networks involved in anther development.

Ascorbate peroxidases (APXs) are heme peroxidases involved in the control of hydrogen peroxide levels and signal transduction pathways related to development and stress responses. Here, a total of 238 APX, 30 APX-related (APX-R), and 34 APX-like (APX-L) genes were identified from 24 species from the Poaceae family. Phylogenetic analysis of APX indicated five distinct clades, equivalent to cytosolic (cAPX), peroxisomal (pAPX), mitochondrial (mitAPX), stromal (sAPX), and thylakoidal (tAPX) isoforms. Duplication events contributed to the expansion of this family and the divergence times. Different from other APX isoforms, the emergence of Poaceae mitAPXs occurred independently after eudicot and monocot divergence. Our results showed that the constitutive silencing of mitAPX genes is not viable in rice plants, suggesting that these isoforms are essential for rice regeneration or development. We also obtained rice plants silenced individually to sAPX isoforms, demonstrating that, different to plants double silenced to both sAPX and tAPX or single silenced to tAPX previously obtained, these plants do not show changes in the total APX activity and hydrogen peroxide content in the shoot. Among rice plants silenced to different isoforms, plants silenced to cAPX showed a higher decrease in total APX activity and an increase in hydrogen peroxide levels. These results suggest that the cAPXs are the main isoforms responsible for regulating hydrogen peroxide levels in the cell, whereas in the chloroplast, this role is provided mainly by the tAPX isoform. In addition to broadening our understanding of the core components of the antioxidant defense in Poaceae species, the present study also provides a platform for their functional characterization.

The diversity of diacylglycerol acyltransferases (DGATs) indicates alternative roles for these enzymes in plant metabolism besides triacylglycerol (TAG) biosynthesis. In this work, we functionally characterized castor bean (Ricinus communis L.) DGATs assessing their subcellular localization, expression in seeds, capacity to restore triacylglycerol (TAG) biosynthesis in mutant yeast and evaluating whether they provide tolerance over free fatty acids (FFA) in sensitive yeast. RcDGAT3 displayed a distinct subcellular localization, located in vesicles outside the endoplasmic reticulum (ER) in most leaf epidermal cells. This enzyme was unable to restore TAG biosynthesis in mutant yeast; however, it was able to outperform other DGATs providing higher tolerance over FFA. RcDAcTA subcellular localization was associated with the ER membranes, resembling RcDGAT1 and RcDGAT2, but it failed to rescue the long-chain TAG biosynthesis in mutant yeast, even with fatty acid supplementation. Besides TAG biosynthesis, our results suggest that RcDGAT3 might have alternative functions and roles in lipid metabolism.

- Growth Regulating Factors (GRFs) comprise a transcription factor family with important functions in plant growth and development. They are characterized by the presence of QLQ and WRC domains, responsible for interaction with proteins and DNA, respectively. The QLQ domain is named due to the similarity to a protein interaction domain found in the SWI2/SNF2 chromatin remodeling complex. Despite the occurrence of the QLQ domain in both families, the divergence between them had not been further explored. Here, we show evidence for GRF origin and determined its diversification in angiosperm species. Phylogenetic analysis revealed 11 well-supported groups of GRFs in flowering plants. These groups were supported by gene structure, synteny, and protein domain composition. Synteny and phylogenetic analyses allowed us to propose different sets of probable orthologs in the groups. Besides, our results, together with functional data previously published, allowed us to suggest candidate genes for engineering agronomic traits. In addition, we propose that the QLQ domain of GRF genes evolved from the eukaryotic SNF2 QLQ domain, most likely by a duplication event in the common ancestor of the Charophytes and land plants. Altogether, our results are important for advancing the origin and evolution of the GRF family in Streptophyta.

sn-Glycerol-3-phosphate 1-O-acyltransferase (GPAT) is an important enzyme that catalyzes the transfer of an acyl group from acyl-CoA or acyl-ACP to the sn-1 or sn-2 position of sn-glycerol-3-phosphate (G3P) to generate lysophosphatidic acids (LPAs). The functional studies of GPAT in plants demonstrated its importance in controlling storage and membrane lipid. Identifying genes encoding GPAT in a variety of plant species is crucial to understand their involvement in different metabolic pathways and physiological functions. Here, we performed genome-wide and evolutionary analyses of GPATs in plants. GPAT genes were identified in all algae and plants studied. The phylogenetic analysis showed that these genes group into three main clades. While clades I (GPAT9) and II (soluble GPAT) include GPATs from algae and plants, clade III (GPAT1-8) includes GPATs specific from plants that are involved in the biosynthesis of cutin or suberin. Gene organization and the expression pattern of GPATs in plants corroborate with clade formation in the phylogeny, suggesting that the evolutionary patterns is reflected in their functionality. Overall, our results provide important insights into the evolution of the plant GPATs and allowed us to explore the evolutionary mechanism underlying the functional diversification among these genes.

Heavy metals are natural non-biodegradable constituents of the Earth's crust that accumulate and persist indefinitely in the ecosystem as a result of human activities. Since the industrial revolution, the concentration of cadmium, arsenic, lead, mercury and zinc, amongst others, have increasingly contaminated soil and water resources, leading to significant yield losses in plants. These issues have become an important concern of scientific interest. Understanding the molecular and physiological responses of plants to heavy metal stress is critical in order to maximize their productivity. Recent research has extended our view of how plant hormones can regulate and integrate growth responses to various environmental cues in order to sustain life. In the present review we discuss current knowledge about the role of the plant growth hormones abscisic acid, auxin, brassinosteroid and ethylene in signaling pathways, defense mechanisms and alleviation of heavy metal toxicity.

Drought limits wheat production in the Brazilian Cerrado biome. In order to search for candidate genes associated to the response to water deficit, we analyzed the gene expression profiles, under severe drought stress, in roots and leaves of the cultivar MGS1 Aliança, a well-adapted cultivar to the Cerrado. A set of 4,422 candidate genes was found in roots and leaves. The number of down-regulated transcripts in roots was higher than the up-regulated transcripts, while the opposite occurred in leaves. The number of common transcripts between the two tissues was 1,249, while 2,124 were specific to roots and 1,049 specific to leaves. Quantitative RT-PCR analysis revealed a 0.78 correlation with the expression data. The candidate genes were distributed across all chromosomes and component genomes, but a greater number was mapped on the B genome, particularly on chromosomes 3B, 5B and 2B. When considering both tissues, 116 different pathways were induced. One common pathway, among the top three activated pathways in both tissues, was starch and sucrose metabolism. These results pave the way for future marker development and selection of important genes and are useful for understanding the metabolic pathways involved in wheat drought response.

Since the first diacylglycerol acyltransferase (DGAT) gene was characterized in plants, a number of studies have focused on understanding the role of DGAT activity in plant triacylglycerol (TAG) biosynthesis. DGAT enzyme is essential in controlling TAGs synthesis and is encoded by different genes. DGAT1 and DGAT2 are the two major types of DGATs and have been well characterized in many plants. On the other hand, the DGAT3 and WS/DGAT have received less attention. In this study, we present the first general view of the presence of putative DGAT3 and WS/DGAT in several plant species and report on the diversity and evolution of these genes and its relationships with the two main DGAT genes (DGAT1 and DGAT2). According to our analyses DGAT1, DGAT2, DGAT3 and WS/DGAT are very divergent genes and may have distinct origin in plants. They also present divergent expression patterns in different organs and tissues. The maintenance of several types of genes encoding DGAT enzymes in plants demonstrates the importance of DGAT activity for TAG biosynthesis. Evolutionary history studies of DGATs coupled with their expression patterns help us to decipher their functional role in plants, helping to drive future biotechnological studies.

Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurination of a specific adenine in rRNA. The RIP family members are classified as type I RIPs that contain an RNA-N-glycosidase domain and type II RIPs that contain a lectin domain (B chain) in addition to the glycosidase domain (A chain). In this work, we identified 30 new plant RIPs and characterized 18 Ricinus communis RIPs. Phylogenetic and functional divergence analyses indicated that the emergence of type I and II RIPs probably occurred before the monocot/eudicot split. We also report the expression profiles of 18 castor bean genes, including those for ricin and agglutinin, in five seed stages as assessed by quantitative PCR. Ricin and agglutinin were the most expressed RIPs in developing seeds although eight other RIPs were also expressed. All of the RIP genes were most highly expressed in the stages in which the endosperm was fully expanded. Although the reason for the large expansion of RIP genes in castor beans remains to be established, the differential expression patterns of the type I and type II members reinforce the existence of biological functions other than defense against predators and herbivory.

When plants are exposed to stressful environmental conditions, the production of Reactive Oxygen Species (ROS) increases and can cause significant damage to the cells. Antioxidant defenses, which can detoxify ROS, are present in plants. A major hydrogen peroxide detoxifying system in plant cells is the ascorbate-glutathione cycle, in which, ascorbate peroxidase (APX) enzymes play a key role catalyzing the conversion of H(2)O(2) into H(2)O, using ascorbate as a specific electron donor. Different APX isoforms are present in distinct subcellular compartments, such as chloroplasts, mitochondria, peroxisome, and cytosol. The expression of APX genes is regulated in response to biotic and abiotic stresses as well as during plant development. The APX responses are directly involved in the protection of plant cells against adverse environmental conditions. Furthermore, mutant plants APX genes showed alterations in growth, physiology and antioxidant metabolism revealing those enzymes involvement in the normal plant development.

Environmental stresses caused by either abiotic or biotic factors greatly affect agriculture. As for soybean [Glycine max (L.) Merril], one of the most important crop species in the world, the situation is not different. In order to deal with these stresses, plants have evolved a variety of sophisticated molecular mechanisms, to which the transcriptional regulation of target-genes by transcription factors is crucial. Even though the involvement of several transcription factor families has been widely reported in stress response, there still is a lot to be uncovered, especially in soybean. Therefore, the objective of this study was to investigate the role of bHLH and trihelix-GT transcription factors in soybean responses to environmental stresses. Gene annotation, data mining for stress response, and phylogenetic analysis of members from both families are presented herein. At least 45 bHLH (from subgroup 25) and 63 trihelix-GT putative genes reside in the soybean genome. Among them, at least 14 bHLH and 11 trihelix-GT seem to be involved in responses to abiotic/biotic stresses. Phylogenetic analysis successfully clustered these with members from other plant species. Nevertheless, bHLH and trihelix-GT genes encompass almost three times more members in soybean than in Arabidopsis or rice, with many of these grouping into new clades with no apparent near orthologs in the other analyzed species. Our results represent an important step towards unraveling the functional roles of plant bHLH and trihelix-GT transcription factors in response to environmental cues.