Translational control is a widespread mechanism that allows the cell to rapidly modulate gene expression in order to provide flexibility and adaptability to eukaryotic organisms. We applied translating ribosome affinity purification combined with RNA sequencing to characterize translational regulation of mRNAs at early stages of the nitrogen-fixing symbiosis established between Medicago truncatula and Sinorhizobium meliloti. Our analysis revealed a poor correlation between transcriptional and translational changes and identified hundreds of regulated protein-coding and long noncoding RNAs (lncRNAs), some of which are regulated in specific cell types. We demonstrated that a short variant of the lncRNA Trans-acting small interference RNA3 (TAS3) increased its association to the translational machinery in response to rhizobia. Functional analysis revealed that this short variant of TAS3 might act as a target mimic that captures microRNA390, contributing to reduce trans acting small interference Auxin Response Factor production and modulating nodule formation and rhizobial infection. The analysis of alternative transcript variants identified a translationally upregulated mRNA encoding subunit 3 of the SUPERKILLER complex (SKI3), which participates in mRNA decay. Knockdown of SKI3 decreased nodule initiation and development, as well as the survival of bacteria within nodules. Our results highlight the importance of translational control and mRNA decay pathways for the successful establishment of the nitrogen-fixing symbiosis.

This study evaluated the potential of lambari (Astyanax altiparanae) as a pituitary donor for hormone-induced spawning in fish. The effectiveness of the extracted hormone was demonstrated over four consecutive years, successfully inducing spawning in captive lambari as well as in two other rheophilic species, curimbatá (Prochilodus lineatus) and tambaqui (Colossoma macropomum). When administered in the same manner as crude carp pituitary extract, a total dose of 6 mg·kg⁻¹, divided into two applications (10% + 90%), proved to be effective, since spawning was obtained in the three tested species. Under the applied management conditions, donor fish maintained a gonadosomatic index of approximately 15%, with ovaries predominantly composed of mature vitellogenic oocytes. These females exhibited basal levels of estradiol (around 0.9 ng.ml-1) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) (around 0.2 ng.ml-1), along with stable lhβ expression levels among different baths and between males and females. The lambari pituitary extract, when injected into females of the same species, induced a significant increase in 17,20β-P levels from approximately 0.2 to 1.0 ng·ml⁻¹. The use of lambari pituitary extract confirms that donor fish, both males and females, must be reproductively mature and in the breeding season. To our knowledge, most previous studies on extract donors are based on wild donors, making this one of the few that describe their physiological characteristics under aquaculture conditions. Low rearing densities seem to be crucial for obtaining a potent extract, although fish from the grow-out phase may also be suitable, a possibility that still requires evaluation. Our findings highlight the potential of lambari pituitary glands as a valuable alternative for hormone-induced spawning in small and medium-sized fish species, supported by their rapid maturation (4 months), low trophic level, increasing commercial production, and the prospect of using canned lambari to efficiently recover pituitary glands from fish heads.