Allelic variation in rice Fertilization Independent Endosperm 1 contributes to grain width under high night temperature stress.

Balpreet K Dhatt,Larissa Irvin,Paul Staswick,Gota Morota,Hongfeng Yu,Puneet Paul,Waseem Hussain,Argelia Lorence,Jaspreet Sandhu,Maria Arlene Adviento‐Borbe,Harkamal Walia,Feiyu Zhu

doi:10.1111/nph.16897

Abstract

Summary A higher minimum (night‐time) temperature is considered a greater limiting factor for reduced rice yield than a similar increase in maximum (daytime) temperature. While the physiological impact of high night temperature (HNT) has been studied, the genetic and molecular basis of HNT stress response remains unexplored.We examined the phenotypic variation for mature grain size (length and width) in a diverse set of rice accessions under HNT stress. Genome‐wide association analysis identified several HNT‐specific loci regulating grain size as well as loci that are common for optimal and HNT stress conditions.A novel locus contributing to grain width under HNT conditions colocalized with Fie1, a component of the FIS‐PRC2 complex. Our results suggest that the allelic difference controlling grain width under HNT is a result of differential transcript‐level response of Fie1 in grains developing under HNT stress.We present evidence to support the role of Fie1 in grain size regulation by testing overexpression (OE) and knockout mutants under heat stress. The OE mutants were either unaltered or had a positive impact on mature grain size under HNT, while the knockouts exhibited significant grain size reduction under these conditions.

Highlights

Much of the extraordinary period of exponential crop productivity over the second half of the 20th century is owed to the success of the Green Revolution (Wik et al, 2008; Pingali, 2012; BaileySerres et al, 2019)
Seven accessions had high sensitivity for these two traits under high night temperature (HNT) stress relative to control conditions (Table S3). This suggested that tolerance to HNT stress for grain length and width traits is probably determined independently in rice (Philipp et al, 2018) as there are very few accessions that can maintain both grain length and width under HNT stress conditions
The four major and one minor allele accessions did not have an obvious starch packaging defect (Fig. S12). These results suggest that the allelic variation associated with Fertilization Independent Endosperm 1 (Fie1), which results in differential transcript abundance, could be a contributing factor in determining chalkiness under HNT stress conditions

Summary

Introduction

Much of the extraordinary period of exponential crop productivity over the second half of the 20th century is owed to the success of the Green Revolution (Wik et al, 2008; Pingali, 2012; BaileySerres et al, 2019). Despite increasing land scarcity and rising population, the development of high-yielding cultivars and improved agronomic practices have substantially decreased food deficits (Foley et al, 2011; Pingali, 2012). These improvements have reduced poverty and malnourishment, sustaining these gains will require even greater innovations to address the present-day challenges in agriculture. In this context, climate change, especially the rising temperatures, threatens crop productivity (Porter & Gawith, 1999; Zhao et al, 2017). It has been shown that Tmin has increased more sharply than Tmax for some of the major rice-growing regions of the world (Zhou et al, 2004; Padma Kumari et al, 2007)

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