The functional analysis of SlNCED1 in tomato pollen development.

Abscisic acid (ABA) regulates plant growth and development, but the role of ABA in the development of reproductive organs in tomato has rarely been addressed. In the present study, the role of ABA in the regulation of male and female gametogenesis as well as pollen development and germination is tested in tomato. qRT-PCR and in situ hybridization analysis of 9-cis-epoxycarotenoid dioxygenase (SlNCED1), a key enzyme in the ABA biosynthetic pathway, showed high expression of SlNCED1 primarily in the meristem during gametogenesis and mainly in ovule, stigma, anther/pollen and vascular tissues during floral organ development. SlNCED1 expression and ABA accumulation in anther peak at stages 13-14, suggesting that ABA plays a role in the primary formation of pollen grains. Over expression and suppression of SlNCED1 led to the abnormal development of anther/pollen, especially in SlNCED1-OE lines, which have serious pollen deterioration. The percentage of pollen germination in wild type is 91.47%, whereas it is 6.85% in OE transgenic lines and 38.4% at anthesis in RNAi lines. RNA-Seq of anthers shows that SlNCED1-OE can significantly enhance the expression of SlPP2Cs and down-regulate the expression of SlMYB108 and SlMYB21, which are anther/flower-specific transcriptional factors in tomato. Finally, anther transcriptome data indicate that SlNCED1 is involved in ABA-mediated regulation in pollen/anther metabolism, cell wall modification, and transcription levels. These results support an important role for ABA in the development of reproductive organs in tomato and contribute to the elucidation of the underlying regulatory mechanisms.