Strigolactones enhance apple drought resistance via the MsABI5-MsSMXL1-MsNAC022 cascade

Abstract

Drought stress limits plant growth, development, and yield in apple (Malus). Strigolactones (SLs) work with abscisic acid (ABA) to improve drought resistance in plants, but how this synergistic mechanism functions remains unclear. Here, we determined that SLs promote drought resistance in apple in an ABSCISIC ACID INSENSITIVE5 (MsABI5)-related manner. During drought stress of a wild apple species (Malus sieversii), SLs enhanced the expression of MsABI5, encoding a major transcription factor involved in ABA signaling. MsABI5 bound to the promoter of the gene encoding delta-1-pyrroline-5-carboxylate synthase (MsP5CS2.2), upregulating its expression and thereby enhancing proline accumulation and drought resistance. In addition, MsABI5 suppressed the expression of MsSMXL1, encoding a major transcriptional repressor involved in SL signaling. MsSMXL1 interacted with MsNAC022 instead of MsABI5 to repress the transactivation activity of MsNAC022. MsNAC022 was upregulated by MsABI5, and MsNAC022 directly promoted MsP5CS2.2 expression to enhance proline accumulation and drought resistance. These findings suggest that MsSMXL1 and MsNAC022 comprise a regulatory node downstream of MsABI5 during drought stress in apple. Together, our findings suggest that in apple, SLs increase drought resistance by activating the MsABI5-MsSMXL1-MsNAC022 cascade.

Acknowledgements

We are grateful to Professor Bingbing Li (China Agricultural University, China) for her continued guidance and support. This work is supported by the Nation Key Research and Development Program of China (Grant No. 2022YFD1200501) and the National Natural Science Foundation of China (Grant No. 32272686), the Construction of Beijing Science and Technology Innovation and Service Capacity in Top Subjects (Grant No. CEFF-PXM2019_014207_000032), and the 2115 Talent Development Program of China Agricultural University.

Author Contributions

X.Z., P.Y., and T.L. designed the experiments and wrote the manuscript. B.D. and M.T. performed the plant material treatment. Y.X. and Q.Y. constructed plasmids. S.G. and Q.Z performed RNA extraction and analysis of gene relative expression. X.W. and Y.Y. determined proline, MDA, and chlorophyll. Z.W., S.W., and W.L. purified proteins used in this research.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflict of interest statement

The authors declare that they have no conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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