Differentiation of the High Night Temperature Response in Leaf Segments of Rice Cultivars with Contrasting Tolerance.

Stephanie Schaarschmidt,Joachim Kopka,Alexander Erban,Ellen Zuther,Ulrike Glaubitz

doi:10.3390/ijms221910451

Stephanie Schaarschmidt, Joachim Kopka + Show 3 more

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https://doi.org/10.3390/ijms221910451

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Abstract

High night temperatures (HNT) affect rice yield in the field and induce chlorosis symptoms in leaves in controlled chamber experiments. However, little is known about molecular changes in leaf segments under these conditions. Transcript and metabolite profiling were performed for leaf segments of six rice cultivars with different HNT sensitivity. The metabolite profile of the sheath revealed a lower metabolite abundance compared to segments of the leaf blade. Furthermore, pre-adaptation to stress under control conditions was detected in the sheath, whereas this segment was only slightly affected by HNT. No unique significant transcriptomic changes were observed in the leaf base, including the basal growth zone at HNT conditions. Instead, selected metabolites showed correlations with HNT sensitivity in the base. The middle part and the tip were most highly affected by HNT in sensitive cultivars on the transcriptomic level with higher expression of jasmonic acid signaling related genes, genes encoding enzymes involved in flavonoid metabolism and a gene encoding galactinol synthase. In addition, gene expression of expansins known to improve stress tolerance increased in tolerant and sensitive cultivars. The investigation of the different leaf segments indicated highly segment specific responses to HNT. Molecular key players for HNT sensitivity were identified.

Highlights

Rice (Oryza sativa L.) is a staple food for more than half of the world’s population and plays an important role in ensuring future food security, especially in Asia [1], Africa and the American continent [2]
Metabolic profiles of whole leaves were clearly distinct between cultivars with different high night temperature” (HNT) sensitivity levels [15,22], but nothing is known about the detailed HNT response of different leaf segments
Six rice cultivars from two subspecies and with contrasting sensitivity to HNT were selected for an independent investigation of the HNT response in different leaf segments

Summary

Introduction

Rice (Oryza sativa L.) is a staple food for more than half of the world’s population and plays an important role in ensuring future food security, especially in Asia [1], Africa and the American continent [2]. The global mean surface temperature has risen by an average of 0.85 ◦ C and current models predict an increase of up to 3.7 ◦ C by 2100 [3,4]. This temperature increase develops asymmetrically with a faster rise in the global night-time minimum compared to global daytime maximum temperature, leading to “high night temperature” (HNT) conditions [5,6,7]. Chlorosis scoring allows a classification of HNT sensitivity already in the early vegetative stage and was used previously to cluster twelve rice cultivars into

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