Physiological and TMT-based quantitative proteomic responses of barley to aluminium stress under...

Barley (Hordeum vulgare L.) is one of the most important cereal crop in the world, and is also the one being seriously affected by heavy metals, particularly aluminium (Al). Keeping in view the utility of barley as food, fodder and raw material for traditional beer brewing, the top-notch quality and higher production of this crop must be sustained. Phosphorus (P) has a quintessential role in plant growth with a potential to relieve symptoms caused by Al poisoning. Displaying a phytopromotive and stress alleviatory potential, Piriformospora indica (P. indica) can improve the stress tolerance in crops. Several studies have been conducted to evaluate the mechanism of Al translocation in a variety of crops including barley, however, the bio-remediative studies related to detoxification and/or sequestration of metals are scarce. Therefore, the current study was carried out to elucidate the tolerance mechanism of an Al-sensitive barley cultivar ZU9 following the colonization with P. indica and exogenous P supply by physio-biochemical, elemental, leaf ultrastructural and root proteome analyses. When compared to the Al alone treated counterparts, the Al + P + P.i treated plants exhibited 4.1-, 1.38-, 2.7 and 1.35-fold improved root and shoot fresh and dry weights, respectively. With the provision of additional phosphorus, the content of P in the root and shoot for Al + P + P.i group was reportedly higher (71.6% and 49.5%, respectively) as compared to the control group. Moreover, inoculation of P. indica combined with P improved barley leaves' cell arrangement and also maintained normal cell wall shape. The root protemics experiment was divided into three groups: Al, Al + P.i and Al + P + P.i. In total, 28, 598, and 823 differentially expressed proteins were found in Al + P.i vs. Al and Al + P + P.i vs. Al, and phenylpropanoid biosynthesis was the most prominently enriched pathway, which contributed significantly to the recuperating effects of P-P. indica interaction. Conslusively, it was found that the percentage of protein related to peroxidase was 70/359 (Al + P + P.i vs. Al) and 92/447 (Al + P + P.i vs. Al + P.i), respectively, which indicated that P. indica in combination with P might be involved in the regulation of peroxidases, increasing the adaptability of barley plants by enhanced reactive oxygen species (ROS) scavenging mechansism.