Molecular mechanisms of drought stress tolerance that underlie the stay green trait in Sorghum bicolor

Abstract

Drought stress is a major issue for food security, affecting yield production, crop survival and agricultural land quality. Sorghum bicolor is a vital food crop for semi-arid and arid regions, and is also used as a biofuel and as animal fodder. It is extremely well adapted for drought-prone climates and is used extensively as a model for investigating drought tolerance mechanisms. Several varieties display a ‘stay green’ trait in which leaf chlorophyll content and photosynthetic activity is maintained for longer under water limiting conditions, improving survival rates and maintaining higher grain yields under stress.
Two-dimensional gel electrophoresis was used to compare the proteomes of a stay green sorghum variety (B35) and a senescent variety (R16). Alteration in the levels of several proteins were identified between the two lines. Identification and functional characterisation of differentially expressed genes and proteins could enhance our understanding of the processes that underlie the stay green trait in sorghum and identify targets for selective breeding.
SDIR1 homologs in several species have frequently been associated with drought tolerance and stay green mechanisms. Wheat transgenic lines overexpressing SbSDIR1 were analysed for the acquisition of stay green associated characteristics. Transgenic lines were found to display differences in transpiration, ABA-induced gene expression, tiller development and senescence timing suggesting it plays a key role in these processes. Further validation of the phenotype of the SbSDIR1 overexpressing lines and functional characterisation of other candidate genes will contribute to our understanding of the drought tolerance mechanisms in sorghum.