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

Arindam Ghatak,Xiaoliang Sun,Sridharan Jegadeesan,Weimin Li,Luis Valledor,Prasad Bajaj,Palak Chaturvedi,Kristina Gruden,Gert Bachmann,Mitra Mohammadi Bazargani,Wolfram Weckwerth,Rajeev K Varshney,Živa Ramšak

doi:10.3389/fpls.2020.600278

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.

Highlights

Feeding nine billion people with balanced nutritional diet under unpredictable severe weather events is a challenging task
We have identified all significant enzymes associated with the C4 pearl millet NAD-malic enzyme (NAD-ME) subtype photosynthesis under control and drought stress in both the genotypes wheat with different abundance level (Figure 7 and Supplementary Figure S6)
We suggest several strategies for engineering enhanced tolerance in the crop plants under drought stress: (1) Identification and mapping of quantitative trait loci (QTL) for root length in cereal crops as it is an important trait for survival under drought stress

Summary

Introduction

Feeding nine billion people with balanced nutritional diet under unpredictable severe weather events is a challenging task. To alleviate the food crisis, efforts are ongoing to engineer C4 traits into C3 crop species, which can massively increase C3 crop yields (von Caemmerer et al, 2012; Weissmann and Brutnell, 2012; Wang et al, 2014; Rangan et al, 2016). Such efforts require an improved understanding of the physiological traits (such as deep rooting, stay-green, and senescence etc.) and system-level analysis to identify the regulatory networks underlying these physiological traits under abiotic stress condition in a comparative manner

Methods

Results

Discussion

Conclusion