SlARF3, A Tomato Auxin Response Gene, Plays Important Role In Tric Home Formation

Trichomes are appendages originating from the aerial epidermal cells of leaves, stems, and floral organs in plants. Trichomes increasing tolerance to diverse environmental cues and abiotic stress.But, the knowledge of the molecular regulatory mechanisms of tomato trichome is less studied. The auxin response factor(ARF) genes encode a large family of proteins involving in auxin signaling transduction. Most members of ARF family consist of an amino-terminal DNA binding domain(DBD), a middle region that functions as repression domain(RD) or an activation domain(AD),and a carboxy-terminal dimerization domain(CTD) that is responsible for the formation of either ARF/ARF homo- and heterodimers or ARF/Aux-IAA hetero-dimers. Studies have shown the ARF genes play a important role in fruit set, vascular development, fruit ripening, root growth and flower Abscission.In this study,we researched the functions of ARF genes in the formation and development of tomato trichome.1. Expression analysis showed that Sl ARF3, Sl ARF4, Sl ARF6 and Sl ARF10 have high expression level in trichomes.2. The physiological function of Sl ARF3 was studied by using RNA interference(RNAi) strategy. The Sl ARF3 down-regulated plants exhibited the decreased thickness of leaf and density of epidermal pavement cells. The number of shoot xylem cells was also decreased in Sl ARF3 down-regulated lines. The density of type I, V and VI trichomes of leaves were obviously reduced in Sl ARF3-suppressed plants, indicating the important role of Sl ARF3 in trichome formation in tomato.3. Furthermore, RNA-sequencing(RNA-Seq) analysis identified 51 differential expression genes(DEGs) belonging to 14 TF families, such as MYB, b HLH, WD40 and C2H2 zinc finger. 28 DEGs were involved in the metabolism and signaling transduction of phytohormones, such as auxin, ethylene and gibberellin.Taken together, out results demonstrated the Sl ARF3 play important role in trichome formation. Furthermore transcription factor: such as MYB, b HLH, WD40 and C2H2 zinc finger and phytohormones: such as auxin, ethylene also have a significant influence in the formation and development of tomato trichome. Our study found that similar molecular regulatory mechanisms regulate trichome ormation between tomato and Arabidopsis.