Physiological and Proteomic Signatures Reveal Mechanisms of Superior Drought Resilience in Pearl Millet Compared to Wheat

Abstract

Presently, pearl millet and wheat are belonging to highly important cereal crops. Pearl millet, however, is an under-utilized crop, despite its superior resilience to drought and heat stress in contrast to wheat. To investigate this in more detail, we performed comparative physiological screening and large scale proteomics of drought stress responses in drought-tolerant and susceptible genotypes of pearl millet and wheat. These chosen genotypes are widely used in breeding and farming practices. The physiological responses demonstrated large differences in the regulation of root morphology and photosynthetic machinery, revealing a stay-green phenotype in pearl millet. Subsequent tissue-specific proteome analysis of leaves, roots and seeds led to the identification of 12,558 proteins in pearl millet and wheat under well-watered and stress conditions. To allow for this comparative proteome analysis and to provide a platform for future functional proteomics studies we performed a systematic phylogenetic analysis of all orthologues in pearl millet, wheat, foxtail millet, sorghum, barley, brachypodium, rice, maize, Arabidopsis, and soybean. In summary, we define (i) a stay-green proteome signature in the drought-tolerant pearl millet phenotype and (ii) differential senescence proteome signatures in contrasting wheat phenotypes not capable of coping with similar drought stress. These different responses have a significant effect on yield and grain filling processes reflected by the harvest index. Proteome signatures related to root morphology and seed yield demonstrated the unexpected intra- and interspecies-specific biochemical plasticity for stress adaptation for both pearl millet and wheat genotypes. These quantitative reference data provide tissue- and phenotype-specific marker proteins of stress defense mechanisms which are not predictable from the genome sequence itself and have potential value for marker-assisted breeding beyond genome assisted breeding.

Pearl Millet: A Climate-Resilient Nutricereal for Mitigating Hidden Hunger and Provide Nutritional Security

“…Further, it can help design strategies to improve stress tolerance/resistance of pearl millet as well as other related crop plants. Several proteomic studies have been also carried out in pearl millet, which can provide a framework to investigate C 4 photosynthesis in pearl millet in more depth (Ghatak et al, 2016(Ghatak et al, , 2021Weckwerth et al, 2020). A shotgun proteomics approach (GEL-LC-Orbitrap-MS) was used by Ghatak et al (2016) to identify 2,281 proteins from different tissues of pearl millet (root, seed, and leaf) showing significant changes under drought stress condition.…”

Transcriptomic analysis of methyl jasmonate treatment reveals gene networks involved in drought tolerance in pearl millet

“…In wheat ( Triticum aestivum L.), 0.25 µM of MeJA delayed senescence under drought condition 37 . In pearl millet, key characteristics of drought resistance are related to root morphology as well as an efficient photosynthetic machinery 30 . Our results revealed a reduction in chlorophyll content that suggests a loss of photosynthetic pigments or activity.…”

“…These groups of proteins were also up-regulated in the leaves under drought in bean ( Phaseolus vulgaris L. 53 , in wheat ( Triticum aestivum L.) 54 and in maize ( Zea mays) 55 . Furthermore, ribulose bisphosphate carboxylase small chain (Pgl_GLEAN_10020566), a protein identified as associated with a degradation of chlorophyll 30 . Together, they are associated with the processes that underlie the senescence or the stay-green phenotype and overexpressed in SosatC88 by MeJA.…”

“…Comprehensive physiological and proteomic responses of the drought stressed pearl millet revealed significant tissue-specific signatures during the adaptation to drought conditions 29 . In addition, a stay-green phenotype signature in drought-tolerant pearl millet was defined that contributes to a significant effect on yield, grain filling and chlorophyll loss 30 . The present study investigates genes that are differentially expressed after an exogenous MeJA treatment and with a mimic of water deficit by withholding water supply to decipher the molecular basis modulating the response of pearl millet under water scarcity conditions.…”

Lessons Learned from the Studies of Roots Shaded from Direct Root Illumination

“…On the one hand, lateral root growth seems to be rather promoted under salt stress growth conditions to increase root surface area and search for water and nutrients [ 1 ], but it is impaired when the root is exposed to excessive illumination, especially UV-B [ 9 ]. Studying the adaptation of root system architecture under toxic growth conditions, including salt stress and drought, is crucial as the availability of unpolluted soil and water for crop production continuously decreases, leading to devastating crop losses [ 93 , 96 , 97 , 98 ]. To study plant stress responses in soil, Rhizotrons, also known as Rhizoboxes, are used, which still allow monitoring of root growth under controlled conditions [ 42 , 96 , 99 , 100 ].…”