Genome-Wide Identification and Expression Analysis of the MYB Gene Family in Gracilariopsis lemaneiformis to Reveal Potential Members Involved in High-Temperature Stress.

Gracilariopsis lemaneiformis, as an economically important red alga, often suffers high-temperature stress which poses a threat to algal yield and even survival. It is important to achieve new varieties with stable traits and heat tolerance; hence, research on the discovery and functional analysis of high-temperature responsive genes of G. lemaneiformis is significant. MYB (v-myb avian myeloblastosis viral oncogene homolog) gene family is one of the largest transcription factor superfamilies in eukaryotes and has been proved to regulate multiple environmental stresses. However, the identification and comprehensive analysis of the MYB gene family in G. lemaneiformis has rarely been studied. In this study, we identified 18 MYB genes in G. lemaneiformis at the genome-wide level, including 15 1R-MYB/MYB-related, 2 R2R3-MYB, and 1 R1R2R3-MYB members. Among them, GlMYB3, GlMYB4, GlMYB8, GlMYB9, and GlMYB15 were remarkably induced under high temperature and were also upregulated by salicylic acid, methyl jasmonate, or abscisic acid. GlMYB3, GlMYB4, GlMYB9, and GlMYB15 were localized in the nucleus when transiently expressed in Nicotiana benthamiana plants. GlMYB4, as one of the most strongly induced high temperature-associated genes, showed transactivation activity, and the C-terminal was critical for the transactivation activity. By yeast two-hybrid screening, GlMYB4 may interact with three candidate proteins: calcineurin subunit B (CNB), O-linked N-acetylglucosamine transferase (OGT), and cleavage and polyadenylation specificity factor (CPSF) to modulate high temperature tolerance.