biologia plantarum

Biologia Plantarum 63: 134-144, 2019 | DOI: 10.32615/bp.2019.016

Deficiency in phytochromobilin biosynthesis enhances heat-stress-induced impairments to the photosynthetic apparatus in tomato

A.J. Crispim Filho^1,*, A.C. Costa², F.R.R. Alves³, P.F. Batista², A.A. Rodrigues⁴, S.C. Vasconcelos Filho⁴, K.J.T. Nascimento⁵

¹ Departamento de Melhoramento Genético de Plantas, Escola de Agronomia, Universidade Federal de Goiás, Goiânia 74690-900, Goiás, Brazil

² Laboratório de Ecofisiologia e Produtividade Vegetal, Instituto Federal Goiano, Rio Verde 75.901-970, Goiás, Brazil

³ Laboratório de Fisiologia Vegetal, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia 74690-900, Goiás, Brazil

⁴ Laboratório de Anatomia Vegetal, Instituto Federal Goiano, Rio Verde 75.901-970, Goiás, Brazil

⁵ Laboratório de Sementes, Instituto Federal Goiano, Rio Verde 75.901-970, Goiás, Brazil

Plants are continuously exposed to unfavorable environmental conditions, such as heat stress, which negatively affect plant growth and productivity. There is evidence that phytochromes are involved in plant response to different abiotic stresses. We investigated the possible phytochrome-dependent responses to heat stress in photomorphogenic tomato mutants aurea (au, phytochromobilin-deficient, PΦB) and high-pigment 1 (hp1, hyperresponsive to phytochrome-mediated responses), as well as the wild-type Micro-Tom (MT). In comparison with MT, reductions in photosynthetic rate promoted by a high temperature were more pronounced in au, whereas less pronounced in hp1. All genotypes subjected to the heat stress exhibited adjustments in the capture and dissipation of energy, which were indicated by increases in the initial fluorescence and decreases in the maximum photochemical efficiency of photosystem II (PS II). The effective quantum yield of PS II and the apparent electron transport rate showed greatest alterations in the au mutant. In addition, heat-triggered anatomical changes occurred in all genotypes but were most conspicuous in the au mutant, followed by MT. Thus, phytochrome-dependent mechanisms played pivotal roles in the plant responses to the heat stress, and deficiency in phytochromobilin biosynthesis enhanced the heat-induced impairment of photosynthetic performance.

Keywords: aurea mutant, chlorophyll a fluorescence, high-pigment 1 mutant, phytochromes, thermotolerance, Solanum lycopersicum

Accepted: November 15, 2018; Prepublished online: November 15, 2018; Published online: January 19, 2019Show citation