Constitutive gibberellin response in grafted tomato modulates root-to-shoot signaling under drought stress

Abstract

Plants are sessile organisms that must perceive and respond to various environmental constraints throughout their life cycle. Among these constraints, drought stress has become the main limiting factor to crop production around the world. Water deprivation is perceived primarily by the roots, which efficiently signal the shoot to trigger drought responses in order to maximize a plant's ability to survive. In this study, the tomato (Solanum lycopersicum L.) mutant procera (pro), with a constitutive response to gibberellin (GA), and its near isogenic line cv. Micro-Tom (MT), were used in reciprocal grafting under well-watered and water stress conditions to evaluate the role of GA signaling in root-to-shoot communication during drought stress. Growth, oxidative stress, gene expression, water relations and hormonal content were measured in order to provide insights into GA-mediated adjustments to water stress. All graft combinations with pro (i.e. pro/pro, MT/pro and pro/MT) prevented the reduction of growth under stress conditions without a reduction in oxidative stress. The increase of oxidative stress was followed by upregulation of SlDREB2, a drought-tolerance related gene, in all drought-stressed plants. Scions harboring the pro mutation tended to increase the abscisic acid (ABA) content, independent of the rootstock. Moreover, the GA sensitivity of the rootstock modulated stomatal conductance and water use efficiency under drought stress, indicating GA and ABA crosstalk in the adjustment of growth and water economy.

Grafting onto an Appropriate Rootstock Reduces the Impact on Yield and Quality of Controlled Deficit Irrigated Pepper Crops

“…On the other hand, the capacity to maintain sink activity in the vegetative V/N-DI parts could be an adaptive advantage that leads to more shoot growth and bigger yields through regulating source-sink relations [24] with DI. Other mechanisms not associated to maintenance photosynthetic activity have been described to explain the better biomass and yield performance in grafted plants under DI as osmotic adjustment [48], modulation of antioxidant defenses [49] or hormonal signaling [50].…”

Transcriptomic studies reveal a key metabolic pathway contributing to a well-maintained photosynthetic system under drought stress in foxtail millet (Setaria italica L.)

“…Among the DEGs that we identified from three drought-treated cultivars, four genes encoding CAMK kinases were up-regulated, three genes encoding WAK receptor kinases were down-regulated, and seven PP2C genes were up-regulated in all three cultivars ( Table S9 ). Aux/IAA, ETH, and GA are phytohormones playing an important part in maintaining normal plant growth and development, and in reacting to abiotic stresses ( Arraes et al, 2015 ; Gaion et al, 2017 ; Yu et al, 2017 ). Our study detected one down-regulated gene encoding for Aux/IAA, two ETH-encoding genes (one up-regulated and one down-regulated) and three GA-encoding genes (one up-regulated and two down-regulated) in all three drought-treated cultivars ( Table S9 ).…”

Systemic Long-Distance Signaling and Communication Between Rootstock and Scion in Grafted Vegetables

“…Phytohormone crosstalk is also involved in the regulation of growth in grafted vegetables; and GA and ABA have been shown to regulate growth in grafted tomato (Gaion et al, 2018). These studies suggest that phytohormones (ABA, IAA, and CK) may function as long-distance signals in grafted plants.…”

“…Researchers have speculated about the mechanisms of RNA and protein phloem transport/co-transport, in regard to tissue specificity (Wang J. et al, 2017;Kehr and Kragler, 2018), whether specific structural sequences are required (Kim et al, 2001;Haywood et al, 2005;Huang and Yu, 2009;Ham et al, 2009;Zhang W. et al, 2016;Yang et al, 2019), and the role of RNA-binding proteins (Yoo et al, 2004;Ham et al, 2009;Ostendorp et al, 2017). Generally, research on grafted vegetables has mainly focused on stress resistance (Rouphael et al, 2008;Yu et al, 2017), graft compatibility (Ren et al, 2018), hormonal responses (Albacete et al, 2009;Gaion et al, 2018), and long-distance transport signals in vascular systems (Lin et al, 2007;Li et al, 2013;Zhang et al, 2018;Huang et al, 2018). Nevertheless, "omics" analyses are direct and rapid methods of detecting and identifying mobile and differentially expressed substances (Yu et al, 2017), such as DEGs (Xu et al, 2016), DEMs (Ren et al, 2018), and DAPs (Xu et al, 2018) in grafted vegetables; however, results obtained from "omics" datasets need to be verified by combining more biological experiments, such as fluorescence quantitative analysis of gene expression pattern.…”

“…Abscisic acid (ABA) in tomato rootstocks may be transported upward to regulate stomatal closure of scions (Dodd et al, 2009). Furthermore, GA may be produced tomato rootstocks and scions under drought stress (Gaion et al, 2018). However, further investigation using other methods, such as transgenic sequencing and RNA-seq, is needed to determine whether the phenotypic compensation, in mutants whose gene related to phytohormone transport was interfered, caused by grafting is a result of the transport of phytohormones between rootstocks and scions.…”