Banca de DEFESA: INES ARIANE DE PAIVA CANCIO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : INES ARIANE DE PAIVA CANCIO
DATE: 24/02/2026
TIME: 09:00
LOCAL: videoconferência
TITLE:

Humic acid as an inducer of eustress: early transcriptional and metabolic responses in rice roots (Oryza sativa L.)

KEY WORDS:

Plant biostimulants. Priming. Redox signaling.

PAGES: 92
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:

Humic substances (HS) are widely recognized as plant biostimulants, although the molecular mechanisms underlying their mode of action remain poorly understood. Using RNA-seq in rice roots subjected to only four hours of exposure to humic acid (HA), we demonstrated a rapid and robust transcriptional reprogramming, characteristic of a eustress state. HA treatment resulted in the induction of 231 genes, predominantly associated with redox homeostasis, cellular detoxification, and jasmonate-mediated signaling, while only seven genes were repressed. Functional enrichment analyses revealed activation of antioxidant networks, including glutathione and peroxidases, phenylpropanoid metabolism, and jasmonate biosynthesis, as well as the induction of transcription factors from the WRKY and C2H2 families. This coordinated response pattern supports the hypothesis that HA acts as a chemical eustressor, capable of triggering a priming effect without causing immediate deleterious stress, thereby promoting greater resilience to subsequent environmental challenges. To investigate whether this early transcriptional reprogramming translates into functional metabolic adjustments, untargeted metabolomic analysis was performed on roots and leaves at 8 h and 72 h after HA application. Metabolomics revealed a strongly tissue- and time-dependent response, with a predominance of induced metabolites in roots at the early 8 h time point, whereas responses in leaves and at later time points were more discrete and functionally dispersed. Significantly enriched metabolic classes included organic acids, carbohydrate derivatives, amino acids, and peptides, indicating activation of central carbon and nitrogen metabolism, in agreement with the transcriptional processes previously observed. In addition, induction of classes belonging to secondary metabolism, such as phenylpropanoids and alkaloids, was detected, suggesting a state of metabolic preparedness associated with signaling and physiological adaptation. Integration of transcriptomic and metabolomic data indicates that HA triggers a coordinated molecular response, in which early gene reprogramming is followed by consistent metabolic remodeling, characterizing a predominantly root-centered metabolic priming process. These results broaden the understanding of humic acid modes of action and reinforce its role as a bioactive modulator capable of promoting rapid, integrated, and potentially beneficial physiological adjustments that enhance plant resilience to environmental stresses.

COMMITTEE MEMBERS:
Presidente - 2626406 - LEANDRO AZEVEDO SANTOS
Interno - 387406 - RICARDO LUIZ LOURO BERBARA
Externo à Instituição - VINICIUS MIRANDA DE SOUZA - IFRR