Accumulation of proline in vegetative organs of Triticum aestivum (Poaceae) under drought conditions in the early phases of development: a meta-analysis of data

Proline is considered one of the most important osmolytes accumulated by plants in response to stress factors that cause cell dehydration. A significant body of data has been accumulated on changes in the proline content of cultivated plants of different genotypes under osmotic stress. This fully applies to one of the most important cultivated cereals — durum wheat (Triticum aestivum). However, these data lack objective evaluation and systematization. The aim of this study was to conduct a meta-analysis of data on changes in proline content in wheat plants of various genotypes at early phases of development under drought. Only experimental data obtained under controlled growth conditions were selected for processing. Another key criterion for selecting studies for inclusion in the meta-analysis was the availability of objective data on the level of drought tolerance of the studied genotypes. As a result, the ratios of the mean proline content in plants under stress conditions to the mean content in control conditions — ln(R/R) — were determined based on 112 studies presented in 21 journal articles. It was concluded that the proline content in the vegetative organs of T. aestivum under drought increases significantly. At the same time, there was no significant difference in the degree of increase of this indicator in drought-resistant and sensitive genotypes. In other words, the increase in proline content in wheat is a universal response to osmotic stress. The study also separately discusses the interpretation of data related to the enhanced drought tolerance of transformants with modified proline synthesis or catabolism.