Rubisco and Rubisco Activase Play an Important Role in the Biochemical Limitations of Photosynthesis in Rice, Wheat, and Maize under High Temperature and Water Deficit

Abstract

To understand the effect of heat and drought on three major cereal crops, the physiological and biochemical (i.e., metabolic) factors affecting photosynthesis were examined in rice, wheat, and maize plants grown under long-term water deficit (WD), high temperature (HT) and the combination of both stresses (HT-WD). Diffusional limitations to photosynthesis prevailed under WD for the C3 species, rice and wheat. Conversely, biochemical limitations prevailed under WD for the C4 species, maize, under HT for all three species, and under HT-WD in rice and maize. These biochemical limitations to photosynthesis were associated with Rubisco activity that was highly impaired at HT and under HT-WD in the three species. Decreases in Rubisco activation were unrelated to the amount of Rubisco and Rubisco activase (Rca), but were probably caused by inhibition of Rca activity, as suggested by the mutual decrease and positive correlation between Rubisco activation state and the rate of electron transport. Decreased Rubisco activation at HT was associated with biochemical limitation of net CO2 assimilation rate (AN). Overall, the results highlight the importance of Rubisco as a target for improving the photosynthetic performance of these C3 (wheat and rice) and C4 (maize) cereal crops under increasingly variable and warmer climates.

Photosynthesis in non‐foliar tissues: implications for yield

“…Data were collected post-anthesis in glasshouse-grown plants with a Licor 6400XT mounted with a bespoke cuvette ensuring saturating light (1000 lmol m À2 sec À1 ) and a 25°C block temperature. (Scafaro et al, 2012;Scafaro et al, 2016;Perdomo et al, 2017). On the other hand, this 'risky' behaviour might increase the possibility of early ear dehydration under severe terminal stress conditions, although further experimental evidence is required to support this theory.…”

“…For example, increasing stomatal density or aperture could result in increasing assimilation by removing diffusional constraints and increasing the flux of atmospheric CO 2 to the site of carboxylation; however, such an approach would also facilitate the leakage of respiratory CO 2 (Sui et al , ), which has been demonstrated to be of greater importance in some organs. Alternatively, increased stomatal density in wheat ears could improve evaporative cooling, thereby maintaining assimilation rates under elevated temperatures, assuming a similar temperature sensitivity of photosynthesis in wheat ears and leaves (Scafaro et al , ; Scafaro et al , ; Perdomo et al , ). On the other hand, this ‘risky’ behaviour might increase the possibility of early ear dehydration under severe terminal stress conditions, although further experimental evidence is required to support this theory.…”

A Conserved Sequence from Heat-Adapted Species Improves Rubisco Activase Thermostability in Wheat

“…which presumably enables photosynthesis to continue at higher temperatures, considering that the heat-labile nature of Rca is a major limitation on photosynthesis at higher temperatures for many plant species, including wheat (Feller et al, 1998;Crafts-Brandner and Salvucci, 2000;Sage et al, 2008;Perdomo et al, 2017;Kumar et al, 2019). The fact that other species such as cotton (Gossypium hirsutum) and maize (Zea mays; Sánchez de Jiménez et al, 1995;DeRidder and Salvucci, 2007) also induce specific isoforms of Rca in response to heat stress suggests convergent evolution of the induction of heatstable Rca isoforms in response to heat.…”

“…One of the defining characteristics of Rca is that it is a heat-labile protein and in many species dissociates, denatures, and aggregates with even moderate heat application, to a much greater extent than Rubisco (Feller et al, 1998;Salvucci et al, 2001;Salvucci and Crafts-Brandner, 2004). As such, Rca is considered one of the main causes of a decrease in photosynthetic function for plants exposed to supraoptimal temperatures (Crafts-Brandner and Salvucci, 2000;Sage et al, 2008;Busch and Sage, 2017;Perdomo et al, 2017). Improving the thermostability of Rca is therefore considered one of the most promising ways of improving photosynthesis and thus potentially the yield of crops exposed to the detrimental impacts of heat stress (Parry et al, 2011;Carmo-Silva et al, 2015).…”

Thermal acclimation of photosynthetic activity and Rubisco content in two hybrid poplar clones

“…Images were analysed using ImageJ (Rasband, 2016) to determine band densities of each sample. The RuBisCo, RCA and its two isoforms concentration were expressed as relative to the sample representing the highest density (Perdomo et al, 2017; Prins et al, 2008; Ristic et al, 2009).…”