In this study, we identified a gene, OsALDH2B1, that functions as a master regulator of the growth–defense trade-off in rice. The findings provide an example for the genic basis of growth–defense trade-offs in plants and may also have important implication for crop genetic improvement by exploring and modulating these components to achieve a balance between high yield and disease resistance.
In plants, enhanced defense often compromises growth and development, which is regarded as trade-offs between growth and defense. Here we identified a gene, OsALDH2B1, that functions as a master regulator of the growth–defense trade-off in rice. OsALDH2B1 has its primary function as an aldehyde dehydrogenase and a moonlight function as a transcriptional regulator. Loss of function of OsALDH2B1 greatly enhanced resistance to broad-spectrum pathogens, including fungal blast, bacterial leaf blight, and leaf streak, but caused severe phenotypic changes such as male sterility and reduced plant size, grain size, and number. We showed that its primary function as a mitochondrial aldehyde dehydrogenase conditions male fertility. Its moonlight function of transcriptional regulation, featuring both repressing and activating activities, regulates a diverse range of biological processes involving brassinolide, G protein, jasmonic acid, and salicylic acid signaling pathways. Such regulations cause large impacts on the morphology and immunity of rice plants. The versatile functions of OsALDH2B1 provide an example of the genic basis of growth–defense trade-offs in plants.
Activity assays of the OsALDH2B1 protein. Data represent mean ± SEM (n = 3). 2B1, OsALDH2B1. (A) Aldehyde dehydrogenase activity of OsALDH2B1 in total homogenate (Tot.), mitochondria (Mito.), and nuclear (Nucl.) fractions. Protein isolated from total (Tot.) homogenate with IgG (immunoglobulin G) was used as a negative control. (B) Aldehyde dehydrogenase activity assay of OsALDH2B1 mutant proteins. Protein isolated from the total homogenate from rice protoplast transiently expressing GFP with anti-GFP antibody was used as a negative control. (C) The role of Glu316th and Pro322nd in the transcriptional repression activity of OsALDH2B1. OsALDH2B1 variants were fused to GAL4DB-VP16 as effector constructs. Transient gene expression assays were performed in rice protoplast cells. Different letters above the bars indicate differences by a multiple range test at P < 0.05. (D) Putative OsALDH2B1 binding sequences identified using WebLogo. (E) DNA binding activity assay of OsALDH2B1 by EMSA. The red capital letters indicate the putative OsALDH2B1 binding sequences. The blue capital letters represent a random sequence (RS). (F) DNA binding activity of the Glu316th and Pro322nd mutant proteins of OsALDH2B1.