Genome-Wide Investigation of the PLD Gene Family in Tomato: Identification, Analysis, and Expression

Phospholipase Ds (PLDs) are important phospholipid hydrolases in plants that play crucial roles in the regulation of plant growth, development, and stress tolerance. In this study, 14 PLD genes were identified in the tomato genome and were localized on eight chromosomes, and one tandem-duplicated gene pair was identified. According to a phylogenetic analysis, the genes were categorized into four subtypes: SlPLD alpha, beta, and delta belonged to the C2-PLD subfamily, while SlPLD zeta belonged to the PXPH-PLD subfamily. The gene structure and protein physicochemical properties were highly conserved within the same subtype. The promoter of all the SlPLD genes contained hormone-, light-, and stress-responsive cis-acting regulatory elements, but no significant correlation between the number, distribution, and type of cis-acting elements was observed among the members of the same subtype. Transcriptome data showed that the expression of the SlPLD genes was different in multiple tissues. A quantitative RT-PCR analysis revealed that the SlPLD genes responded positively to cold, salt, drought, and abscisic acid treatments, particularly to salt stress. Different expression patterns were observed for different genes under the same stress, and for the same gene under different stresses. The results provide important insights into the functions of SlPLD genes and lay a foundation for further studies of the response of SlPLD genes to abiotic stresses.