Rice withSUB1QTL possesses greater initial leaf gas film thickness leading to delayed perception of submergence stress

Abstract

Background and Aims Submergence tolerance in rice is primarily attributed to SUB1 gene action, but other associated traits such as leaf gas film (LGF) thickness, leaf hydrophobicity, porosity and leaf density have been known to aid submergence tolerance in rice. However, association of these traits with SUB1 QTL is not well worked out. In this study, we aim to investigate (i) whether the presence of SUB1 QTL in the genetic background has any influence on the thickness of the leaf gas film, and (ii) whether removal of it has any impact on stress perception and submergence tolerance in Sub1 and non-Sub1 rice? Methods We examined twelve genotypes (including both Sub1 and non-Sub1 types) for different leaf traits like initial LGF thickness, leaf hydrophobicity tissue porosity and leaf density in order to work out the relation of these traits with SUB1 QTL in rice. Furthermore, we investigated the changes in gene expression profile and different metabolic processes in selected genotypes in the presence and absence of their LGF to study its impact on stress perception and adaptation. Key Results The initial thickness of LGF and hydrophobicity seemed to have a highly positive correlation with the presence of SUB1 QTL in the genetic background of rice; although, other leaf traits like porosity and density seemed to be independent of it. Artificial removal of LGF resulted in partial loss of tolerance showing increased ethylene production and early induction of anoxia related genes (SUB1A-1, ACS5, Ramy3D, ADH1) which manifested symptoms like increased stem elongation, faster chlorophyll and starch breakdown and partial loss of quiescence in SUB1 containing rice genotypes. Stripping of LGF resulted in early and enhanced induction of SUB1A-1 indicating quicker perception of stress. Conclusions The presence of SUB1 in the genetic background positively influences surface hydrophobicity and the concomitant LGF thickness of rice. Furthermore, LGF helps in terms of providing better ethylene ventilation and reduced in planta accumulation, owing to the slowing down of ethylene induced leaf senescence under submergence stress.

The submergence tolerance regulator SUB1A differentially coordinates molecular adaptation to submergence in mature and growing leaves of rice (Oryza sativa L.)

“…The primary function of SUB1A in submergence tolerance is to reduce energy reserve metabolism by limiting ethylene synthesis and responsiveness, suppressing gibberellic acid (GA) responsiveness, and activating brassinosteroid synthesis, thereby restricting shoot elongation and avoiding energy starvation under stress (Barding et al, 2012(Barding et al, , 2013Fukao et al, 2006;Fukao and Bailey-Serres, 2008;Schmitz et al, 2013). In addition to metabolic adjustments, SUB1A increases the thickness of the leaf gas film under submergence, enhancing the surface hydrophobicity of leaves (Chakraborty et al, 2021). Moreover, it has been shown that SUB1A is phosphorylated by mitogen-activated protein kinase 3 (MPK3), and that the presence and activity of MPK3 are correlated with submergence tolerance in rice plants containing SUB1A (Singh and Sinha, 2016).…”

Identification of QTLs for stagnant flooding tolerance in rice employing genotyping by sequencing of a RIL population derived from Swarna × Rashpanjor

“…Rice genotypes tolerant to flooding stress at the germination stage can withstand the stress through overexpression of amylolytic and fermentative enzymes, greater ethylene production, and increased coleoptile growth (Vijayan et al 2018). Whereas rice genotypes capable to tolerate complete submergence restrict ethylene production vis-a-vis gibberellins biosynthesis, and limit the use of non-structural carbohydrates through suppressing amylolytic enzyme activity (Chakraborty et al 2021a). Therefore, QTLs/genes for stagnant flooding tolerance could be different from that of submergence or deep-water stresses.…”

Toward Integrated Multi-Omics Intervention: Rice Trait Improvement and Stress Management

“…An important QTL associated with submergence tolerance is SUB1 (submergence 1) (Xu et al, 2006;Fukao and Bailey-Serres, 2008). A recent study affirmed that SUB1 influences concomitant leaf gas film thickness and surface hydrophobicity (Chakraborty et al, 2021). Leaf gas film provides improved ethylene dissipation and decreased in-planta accumulation.…”

“…Leaf gas film provides improved ethylene dissipation and decreased in-planta accumulation. This eventually results in the delay of ethyleneinduced leaf senescence upon submergence stress (Chakraborty et al, 2021). Another flooding stress-related condition involves the exposure of plants to hypoxia.…”