Redox homeostasis at SAM: a new role of HINT protein.

MAIN CONCLUSION: ScHINT1 was identified at sugarcane SAM using subtractive libraries. Here, by bioinformatic tools, two-hybrid approach, and biochemical assays, we proposed that its role might be associated to control redox homeostasis. Such control is important for plant development and flowering transition, and this is ensured with some protein partners such as PAL and SBT that interact with ScHINT1. The shoot apical meristem transition from vegetative to reproductive is a crucial step for plants. In sugarcane (Saccharum spp.), this process is not well known, and it has an important impact on production due to field reduction. In view of this, ScHINT1 (Sugarcane HISTIDINE TRIAD NUCLEOTIDE-BINDING PROTEIN) was identified previously by subtractive cDNA libraries using Shoot Apical Meristem (SAM) by our group. This protein is a member of the HIT superfamily that was composed of hydrolase with an AMP site ligation. To better understand the role of ScHINT1 in sugarcane flowering, here its function in SAM was characterized using different approaches such as bioinformatics, two-hybrid assays, transgenic plants, and biochemical assays. ScHINT1 was conserved in plants, and it was grouped into four clades (HINT1, HINT2, HINT3, and HINT4). The 3D model proposed that ScHINT1 might be active as it was able to ligate to AMP subtract. Moreover, the two-hybrid approach identified two protein interactions: subtilase and phenylalanine ammonia-lyase. The evolutionary tree highlighted the relationships that each sequence has with specific subfamilies and different proteins. The 3D models constructed reveal structure conservation when compared with other PDB-related crystals, which indicates probable functional activity for the sugarcane models assessed. The interactome analysis showed a connection to different proteins that have antioxidative functions in apical meristems. Lastly, the transgenic plants with 35S::ScHINT1_AS (anti-sense orientation) produced more flowers than wild-type or 35S::ScHINT1_S (sense). Alpha-tocopherol and antioxidant enzymes measurement showed that their levels were higher in 35S::ScHINT_S plants than in 35S::ScHINT1_AS or wild-type plants. These results proposed that ScHINT1 might have an important role with other proteins in orchestrating this complex network for plant development and flowering.

Evaluation of Blend Production of Cellulases and Xylanases Using Pretreated and Recycled Carnauba Straw.

Carnauba (Copernicia prunifera) is a Brazilian palm tree used for wax production, which usually generates a large amount of waste. This work evaluated the carnauba waste for cellulase and xylanase production using Trichoderma reesei CCT2768 through a solid-state fermentation (SSF). Carnauba waste was used in its crude form (C-IN), pretreated (C-P) with alkaline hydrogen peroxide (AHP), and also recycled after the SSF process (C-PR). C-IN, C-P, and C-PR were characterized by XRD, FTIR, and SEM. Cellulase and xylanase production was performed by SSF for 72 h, and the enzymatic extracts obtained were mixed each other in different concentrations. FPase, CMCase, and xylanase activities were determined. Trichoderma reesei CCT-2768 has shown high performance to produce cellulases and xylanases. Total cellulase, CMCase, and ß-glycosidase presented a highest activity when C-PPR1 (25% of C-PR and 75% of C-P) was used as a carbon source, with yield of 2.85 U/g, 41.21 U/g, and 2.80 U/g, respectively. The highest xylanase production was achieved when only the pretreated carnauba waste (C-P) was used, with an enzyme activity of 224.93 U/g. Carnauba has shown a promising carbon source capacity to induce the production of cellulolytic and xylanolytic enzymes by using T. reesei CCT2768, promoting the circular and ecofriendly economy, as well as a cost reduction, of the production process of these enzymes.