Genome-Wide Identification and Expression Analysis of the Growth Regulatory Factor (GRF) and Growth-Regulating Interacting Factor (GIF) Gene Families in Cassava

Growth regulatory factors (GRFs) and growth-regulating interacting factors (GIFs) play significant roles in plant growth, development, and environmental stress responses. Previous studies have reported the functions of GRF and GIF genes in model plants such as Arabidopsis and rice. Nevertheless, the GRF and GIF genes remained unexplored in cassava. Cassava (Manihot esculenta Crantz) is an important tropical economic crop. Its starchy storage roots serve as a major source of food and industrial raw materials, while its protein-rich leaves are widely consumed as leafy vegetables in Africa and other regions, offering high nutritional value and significant horticultural potential. This study identified 28 MeGRFs distributed on 13 chromosomes and 5 MeGIFs on 4 chromosomes through bioinformatic analysis and expression profiling. Promoter analysis uncovered cis-acting elements associated with growth, hormone signaling, and biotic stress responses. Under different tissues and biotic (e.g., cassava bacterial blight, CBB) and abiotic (e.g., drought, low temperature) stress conditions, GRF and GIF genes exhibited differential expression patterns. Real-time quantitative PCR analysis showed a significant expression for 11 MeGRFs and 3 MeGIFs under the Xanthomonas phaseoli pv. manihotis (Xpm) treatment. VIGS functional validation demonstrated that MeGRF28 and MeGIF4 could enhance cassava resistance to bacterial blight, and protein–protein interaction network analysis suggested that they may form a core GRF-GIF complex. This study provides a theoretical basis for understanding the functional evolution of the GRF and GIF gene families in cassava and their roles in horticultural trait development and stress resistance mechanisms.