Abstract

Like most crops, sorghum [Sorghum bicolor (L.) Moench] is susceptible to lodging due to severe mechanical forces generated by weather-related phenomena like wind and rain. However, in response to less severe mechanical stimulation, plants may exhibit alterations in growth and development known as thigmomorphogenesis that enhance the plant’s ability to withstand stronger forces. Understanding the mechanisms regulating thigmomorphogenesis may facilitate developing new varieties with greater lodging resistance. The current study investigated the effect of mechanical stimulation on the morphology, anatomy, biomechanical properties, transcriptome expression and endogenous hormones of sweet sorghum stems and if this effect was dependent on the developmental stage of the internodes or the duration of treatment. Mechanical stimulation led to reduced length and increased diameter of internodes, and younger internodes experienced a more pronounced reduction in length. Mechanically-stimulated internodes exhibited lower elastic modulus and flexural stiffness but higher strength (more flexible, stronger) compared to control internodes. Mechanical stimulation also appeared to increase internode vascular bundle size and density as well as the lignification level and a more noticeable increase in lignin content was observed in younger internodes. Transcriptome profiling of internode rind revealed that mechanical stimulation altered the expression of over 900 genes, including a large number of transcription factors and genes related to hormone signaling. The abundances of IAA, GA1 and ABA generally declined following mechanical stimulation, while JA was elevated. Weighted Gene Co-expression Network Analysis (WGCNA) identified three modules highly correlated with mechanical stimulation and morphological and biomechanical traits, which were enriched in pathways associated with cell wall biology, hormone signaling and general stress responses. Additionally, mechanical stimulation-triggered responses were found to be dependent on the developmental stage of the internode and the duration of stimulation. This study provides insights into the underlying mechanisms of plant hormone-regulated thigmomorphogenesis in sorghum stems. The findings from this study may offer opportunities to improve lodging resistance in sorghum and other crops.

Speaker Bio

Dr. Qing Li is a postdoctoral researcher in Dr. Tesfamichael Kebrom’s research group at the Cooperative Agricultural Research Center (CARC). She received her bachelor’s degree in Agricultural Resources and Environmental Science in 2017 at Jilin University, China, and completed her doctoral studies in Molecular & Environmental Plant Sciences at Texas A&M University in August 2023. For her doctoral research, she investigated the physiological and molecular mechanisms that regulate the response of sorghum stems to mechanical stimulation under the supervision of Dr. Scott Finlayson. Qing’s research passion lies in exploring the roles of environmental factors in regulating plant growth and development.