The karrikin receptor KAI2 promotes drought resistance in Arabidopsis thaliana

Abstract

Drought causes substantial reductions in crop yields worldwide. Therefore, we set out to identify new chemical and genetic factors that regulate drought resistance in Arabidopsis thaliana. Karrikins (KARs) are a class of butenolide compounds found in smoke that promote seed germination, and have been reported to improve seedling vigor under stressful growth conditions. Here, we discovered that mutations in KARRIKIN INSENSITIVE2 (KAI2), encoding the proposed karrikin receptor, result in hypersensitivity to water deprivation. We performed transcriptomic, physiological and biochemical analyses of kai2 plants to understand the basis for KAI2-regulated drought resistance. We found that kai2 mutants have increased rates of water loss and drought-induced cell membrane damage, enlarged stomatal apertures, and higher cuticular permeability. In addition, kai2 plants have reduced anthocyanin biosynthesis during drought, and are hyposensitive to abscisic acid (ABA) in stomatal closure and cotyledon opening assays. We identified genes that are likely associated with the observed physiological and biochemical changes through a genome-wide transcriptome analysis of kai2 under both well-watered and dehydration conditions. These data provide evidence for crosstalk between ABA- and KAI2-dependent signaling pathways in regulating plant responses to drought. A comparison of the strigolactone receptor mutant d14 (DWARF14) to kai2 indicated that strigolactones also contributes to plant drought adaptation, although not by affecting cuticle development. Our findings suggest that chemical or genetic manipulation of KAI2 and D14 signaling may provide novel ways to improve drought resistance.

New and Scalable Access to Karrikin (KAR1) and Evaluation of Its Potential Application on Corn Germination

“…Despite other studies indicated that KAR 1 promotes the germination and/or subsequent development of young seedlings, we could not distinctly observe these effects in our studies. In several studies, it is reported that KAR 1 is able to break primary or secondary dormancy in diverse species; in most of the cases it is about a wide range of weeds or A. thaliana .…”

“…Karrikin (KAR 1 ) also named ‘karrikinolide’ was isolated in 2004 from smoke water and identified as a potent germination stimulant as well as controlling early seedling development for a large variety of plant species ( Figure ) . As the well‐known phytohormones strigolactones, karrikins bear a butenolide ring and share similar signaling pathway ( Figure ) .…”

“…Five other karrikin analogs have been so far detected and identified in smoke water named KAR 2 – KAR 6 (structure variation based on their methyl substitution, Figure ), and several synthetic analogs have been prepared and reported in the literature . KAR 1 is by far the major component among the karrikins contained in smoke water and usually the most potent seed germination inducer . Consequently, we decided to concentrate our study on KAR 1 .…”

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

“…Moreover, because MAX2 is shared by both D14‐mediated SL signalling and KAI2‐mediated karrikin signalling pathways (De Cuyper et al, ; Soundappan et al, ), analysis of both D14‐ and KAI2‐mediated pathways might explain why max2 showed a higher water loss rate than what was observed in the SL‐biosynthetic max3 and max4 mutants during dehydration (C. V. Ha et al, ). Indeed, a comparative drought tolerance test of the single d14 and kai2 mutants and kai2 d14 double mutant revealed that all three mutants were sensitive to drought and that the kai2 d14 double mutant plants were more sensitive to drought stress than either of the single mutants under water deprivation (W. Li et al, ). These findings suggest that both SLs, and the yet‐unidentified KL, which binds to and is perceived through KAI2, may act in concert through the checkpoint MAX2 to provide drought tolerance in plants.…”

“…These environmental constraints, both biotic and abiotic, are the leading causes of crop loss and are threats to sustainable agriculture and ecological purposes worldwide (Abdelrahman, Burritt, & Tran, ; AbuQamar, Moustafa, & Tran, ; Millar & Bennett, ; Pandey, Irulappan, Bagavathiannan, & Senthil‐Kumar, ; Suzuki, Rivero, Shulaev, Blumwald, & Mittler, ; Zhu, ). As a survival strategy, plants have evolved various responses to adverse conditions by triggering a series of morpho‐physiological, biochemical, and molecular changes (Abdelrahman, Jogaiah, Burritt, & Tran, ; W. Li et al, ; Mostofa et al, ; Mostofa et al, ; Suzuki et al, ), all of which are perceived and controlled by signal transduction and reprogramming of genetic and metabolic pathways. Phytohormones are integral components for the coordination of such changes to generate sophisticated responses in order to optimize plant growth and development under stress conditions (Abdelrahman, El‐Sayed, Jogaiah, Burritt, & Tran, ; Choudhary, Yu, Yamaguchi‐Shinozaki, Shinozaki, & Tran, ; S. Ha, Vankova, Yamaguchi‐Shinozaki, Shinozaki, & Tran, ; W. Li, Herrera‐Estrella, & Tran, ; Wani, Kumar, Shriram, & Sah, ).…”