Understanding plant responses to drought — from genes to the whole plant

Abstract

In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought — such as phenology, root size and depth, hydraulic conductivity and the storage of reserves — are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype–phenotype gap to be bridged, which is essential for faster progress in stress biology research.

Relationship between water use efficiency (WUE) and production of different wheat genotypes at soil water deficit

“…This fact basically reflected the WUE trend in Fig. 1, but could not for genotypes 1,4,8,9, which showed that other factors such as transpiration and photosynthesis (unpublished papers) influenced TWC. At level 1, genotype 7 had the highest TWC, and genotype 9 the greatest TWC at level 2 and 3, which was also related to its characteristics of flooded origin as mentioned in genotype 10.…”

“…Unlocking the physiological and molecular basis for the plasticity of plant defending metabolism not only provides access to a largely untapped resource of genes and selection markers for breeding enhanced stress tolerance in crops but also ensures improved food security and agricultural sustainable development worldwide [5,8,10,19,32,44,48,52,62].…”

“…Although the obtained transgenic crops (mainly, wheat) by different types of gene technology all exhibit drought resistance to some extent, they have many shortfalls related to agronomical performance and/or development [47,49,53,62,66,68,74]. These results imply that systemical, deeper, and comprehensive understanding of physiological mechanism of crops under drought stresses is not enough to manipulate the physiological regulatory mechanism and take advantage of full this potential for productivity, whose study is the bridge between molecular machinery of drought and anti-drought agriculture, because the performance of genetic potential of crops is expressed by physiological realization in fields [1,2,8,10,53,54]. Towards this aim, many promising methodologies appear, but they should also be linked with field practice [12,13,18,24,29,31,40,51,72].…”

“…Wheat is a staple food for more than 35% of the world population and wheat is also the second grain crop in China, whose production status is directly related to social stability, Chinese survival and sustainable development [13,21,22,30,37,38,59,65]. With progressive global climate change and increasing shortage of water resources and worsening eco-environment, wheat production is influenced greatly [8,38,52]. Many reports have been related to WUE and production and clearly explained the linear relationship between WUE and production in wheat, maize and other plants [21,22,26,36,37,46,41,76], but little is involved in such aspect of different wheat genotypes.…”

Influence of drought on plant performance through changes in belowground tritrophic interactions

“…First, it can directly affect the performance of plants (Chaves, Maroco, & Pereira, 2003), root herbivores (Barnett & Johnson, 2013; Johnson et al., 2010), and natural enemies (Grant & Villani, 2003; Rohde, Moino, Da Silva, Carvalho, & Ferreira, 2010). Second, soil moisture can alter the performance of root herbivores and their natural enemies indirectly via changes in plant chemistry (Khan, Ulrichs, & Mewis, 2010; Vaughan, Block, Christensen, Allen, & Schmelz, 2017).…”