Exogenous abscisic acid treatment regulates protein secretion in sorghum cell suspension cultures

ABSTRACT

Drought stress adversely affects plant growth, often leading to total crop failure. Upon sensing soil water deficits, plants switch on biosynthesis of abscisic acid (ABA), a stress hormone for drought adaptation. Here, we used exogenous ABA application to dark-grown sorghum cell suspension cultures as an experimental system to understand how a drought-tolerant crop responds to ABA. We evaluated intracellular and secreted proteins using isobaric tags for relative and absolute quantification. While the abundance of only ~ 7% (46 proteins) intracellular proteins changed in response to ABA, ~32% (82 proteins) of secreted proteins identified in this study were ABA responsive. This shows that the extracellular matrix is disproportionately targeted and suggests it plays a vital role in sorghum adaptation to drought. Extracellular proteins responsive to ABA were predominantly defense/detoxification and cell wall-modifying enzymes. We confirmed that sorghum plants exposed to drought stress activate genes encoding the same proteins identified in the in vitro cell culture system with ABA. Our results suggest that ABA activates defense and cell wall remodeling systems during stress response. This could underpin the success of sorghum adaptation to drought stress.

Keywords:

• Sorghum
• cell suspension cultures
• ABA
• extracellular matrix
• protein secretion
• secretome
• total soluble protein
• iTRAQ
• drought stress
• gene expression

Acknowledgments

We are grateful to the National Research Foundation (NRF) of South Africa, the Royal Society of London, and the UK Research and Innovation (UKRI) for research funding. D.M. and S.J.M. were supported by NRF postgraduate student bursaries.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

RN and SC designed the experiments and supervised the research. RN wrote the first draft and revised the manuscript with SC. DM. and TG conducted the experiments. APB performed mass spectrometry analysis. SJM and RN analyzed the data. All authors reviewed the manuscript.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15592324.2023.2291618

Additional information

Funding

This work was supported by the NRF of South Africa under Grant [number 113966 and 129884] awarded to RN, the Royal Society-Newton Advanced Fellowship Grant [number NA160140] jointly awarded to RN and SC, and the UKRI grants [number BB/N012623/1 and BB/M028429/1] awarded to SC, and the Royal Society-Newton International Fellowship (NIF\R1\221653) awarded to TG/SC.