Phytochrome B1/B2-dependent changes in tomato anther metabolism under prolonged moderately elevated temperatures

José Laurindo dos Santos Júnior1, Lázaro Eustáquio Pereira Peres2, Magdalena Rossi1, Luciano Freschi1

1. IB/USP, Instituto de Biociências da Universidade de São Paulo; Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, 05508-900, São Paulo, SP, BraziL
2. ESAL/USP, Escola Superior de Agricultura Luiz de Queiroz da Universidade de São Paulo; Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, 13418-900, Piracicaba, SP, Brazil

Pollen maturation and anther development are critically affected by high temperature conditions. In tomato (Solanum lycopersicum L.), phyB-encoding genes SlphyB1 and SlphyB2 play both overlapping and distinct roles at early plant development. However, their specific involvement in anther metabolism under normal and high temperature conditions remains elusive. Here, we investigated the impact of Slphyb1 and Slphyb2 loss-of-function mutations on the metabolism of developing anthers from tomato plants grown under control (25 °C/18 °C day/night) and prolonged moderately elevated temperature stress (METS, 32°C/25 °C day/night) conditions. Anthers were harvested at 6, 3, and 0 days before anthesis (dba), corresponding to vacuolization, bicellular stage and mature pollen stages, respectively. Profiling of polar compounds via GC-MS, followed by hierarchical clustering of the metabolomic data and metabolic pathway analysis, revealed development- and temperature-dependent metabolic alterations in both mutants, with unique impacts of SlphyB1 and SlphyB2 on specific metabolic pathways. Anthers from Slphyb1 showed the most intense and persistent metabolic disruption across various pathways, including carbohydrates (e.g., galactose, sucrose and starch), antioxidants (ascorbate), the citrate cycle, amino acids (e.g., proline, GABA, threonine, aspartate), pyruvate, carbon fixation, arginine, inositol phosphate, flavonoids and phenylpropanoid biosynthesis. In contrast, a more restricted impact of Slphyb2 was observed in control and stressed anther tissues, which were limited to changes in galactose and sucrose metabolisms, and some minor changes in amino acid and flavonoid biosynthesis. These data indicate a critical role for SlphyB1 in maintaining energy balance, increasing antioxidant capacity and other early metabolic programming required for pollen development under METS, whereas SlphyB2 seems to play specific and potentially complementary roles.

Agradecimentos: This study was financed by the São Paulo Research Foundation (FAPESP), Brasil. Process Number #2023/08610-4; 202323/03330-3; 2025/01145-0.