Temperature-mediated shifts in chlorophyll biosynthesis in leaves of chlorophyll b-lacking rice (Oryza sativa L.)

Khiem Minh Nguyen,Jun-Wei Lin,Hoang Chinh Nguyen,Chi-Ming Yang,Szu-Hsien Lin,Tin-Han Shih,Zhi-Wei Yang

doi:10.15835/nbha49212306

Abstract

Extreme temperatures have become a threat to crop yields. To maintain plant growth and yield, chlorophyll (Chl) biosynthesis plays a crucial role in adaptation to temperature stress. This study investigated the influence of temperature on the biosynthesis and characteristics of pigments (Chl a, Chl b, and carotenoids) in the leaves of Chl b-lacking mutant rice (Chlorina 1, ch1) and wild-type rice (Norin No.8, wt). The ch1 showed thinner stacked grana caused by a decrease in thylakoid membranes per granum at 15 °C, whereas the destacked grana were observed at 35 °C after 12 h incubation. However, the grana are stacked normally, along with the absence of Chl b, and a significantly decreased amount of Chl a in both wt and ch1 were observed after heat stress exposure, demonstrating that light-harvesting complex II proteins are involved in grana stacking. Ch1 was sensitive to 15 °C during the first 4 h of incubation but it subsequently adapted to the cold environment. In addition, there were no significant differences in the photosynthesis between wt and ch1 after 12 h incubation at 35 °C. Differentially expressed gene (DEGs) analysis revealed that GluRS expression decreased, which resulted in a decline in Chl biosynthesis in wt and ch1 at 35 °C. At 8 h and 12 h, there were no significant differences in the expression of DEGs involved in Chl biosynthesis and degradation between wt and ch1 at 15 °C. ALAD expression in wt and ch1 at 15 °C decreased until it was undetectable. These findings suggested that ch1 may adapt to temperatures ranging from 15 °C to 35 °C.

Highlights

Extreme temperatures caused by climate change, including cold stress and heat stress, affect the development, growth, and seasonal behaviors of plants, and can impact crop yield (Raza et al, 2019; Ding et al, 2020)
The sensitivities under temperature stress on the Chl biosynthesis mechanism of Chl b-lacking rice remains unclear. To further investigate these characteristics, the present study aimed to examine the influence of growth temperature on physiological characteristics and differentially expressed genes (DEGs) encoding 12 enzymes that play important role in Chl biosynthesis at 15 °C and 35 °C in both wt and ch1 rice
Many studies reported that Chl-deficient mutants of plants such as Morus alba and Arabidopsis thalianaare sensitive to temperatures (Yang et al, 1990; Markwell and Osterman, 1992), this study showed that Chl b-lacking and wild-type rice adapted to environmental temperatures in ranging from 15 °C–35 °C

Summary

Introduction

Extreme temperatures caused by climate change, including cold stress and heat stress, affect the development, growth, and seasonal behaviors of plants, and can impact crop yield (Raza et al, 2019; Ding et al, 2020). Global warming frequently accelerates heat stress, which affects a part of the plant life cycle, photosynthesis and carbon assimilation. A heat-stable enzyme in higher plants involved in carbon assimilation and metabolism in the chloroplast stroma, was found to be inactivated at higher temperatures (Salvucci and Crafts-Brandner, 2004; Sharkey, 2005). The chloroplast was suggested as a key sensor to detect elevated temperatures because it is highly sensitive to damage from heat stress (Yu et al, 2012)

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