The L-type lectin receptor-like kinase GmLecRK-IX negatively regulates drought stress responses in soybean seedlings

Soybean (Glycine max (L.) Merr.), a prominent oilseed crop grown around the world, provides essential resources for the human diet as well as livestock feed. However, drought stress severely impacts soybean yield and quality. The presence of lectin receptor-like kinases (LecRLKs) has been identified as being pivotal to plant development and the manifestation of responses to environmental stresses. Nevertheless, there is a paucity of literature on the involvement of LecRLKs in the response of soybean to drought conditions. In this investigation, we discovered an L-type soybean LecRK-IX gene (Glyma.09G150400) using transcriptomic and proteomic approaches. Quantitative reverse transcription PCR analysis revealed that drought stress significantly elevated GmLecRK-IX gene expression. Subcellular localization results indicated that GmLecRK-IX was localized to the endoplasmic reticulum (ER) and the plasma membrane of Nicotiana benthamiana leaves and Arabidopsis protoplasts. Expression pattern analysis revealed that GmLecRK-IX was predominantly expressed in the roots and seeds. Transgenic Arabidopsis plants overexpressing the GmLecRK-IX gene displayed heightened sensitivity to drought, as evidenced by a decreased survival rate, reduced proline content, and elevated malondialdehyde (MDA) levels following drought stress treatment. Furthermore, the transgenic GmLecRK-IX overexpressed (-OE) lines of soybean exhibited a negative effect on the capacity to withstand drought conditions. The transgenic soybean GmLecRK-IX-OE lines exhibited lower levels of leaf water and proline, a higher rate of water loss, increased MDA content, and reduced activities of antioxidant enzymes. RNA-sequencing analysis further revealed that the GmLecRK-IX-OE lines exhibited altered expression of the genes encoding peroxidase (PRXs) and plasma membrane intrinsic proteins (PIPs) in soybean under drought conditions. Our research has uncovered a novel regulatory mechanism in soybean under drought stress and identified potential target genes for development drought-tolerant soybean varieties.