Identification and expression analysis of transcription factors in the Carallia brachiata genome

<p>Rhizophoraceae has 2 terrestrial genera and 4 marine genera. The intertidal zone in which marine mangroves are located is known for its low oxygen and high salinity. Marine and terrestrial genera have evolved distinct adaptive characteristics, among which viviparous reproduction is the most unique. To investigate the genetic foundations difference underlying the adaptive mechanisms of marine–terrestrial genera, we selected two species from Rhizophoraceae. <em>Kandelia obovata</em> is marine and viviparous, and <em>Carallia brachiata</em> is terrestrial and non-viviparous.<em> </em>We compared their transcriptome of 8 tissues (root, stem, leaf, flower, ovule, fruit, seed, embryo) and found that the mature reproductive organs (fruit, seed, embryo) of <em>K. obovata </em>did not reduce metabolic activity compared to <em>C. brachiata</em>. The reproductive organs of <em>K. obovata</em> were regulated by the same gene set as vegetative organs. This contrasted with <em>C. brachiata</em>. Eight kinds of hormone transduction genes were up-regulated in the seed of <em>K. obovata</em>. Finally, and most importantly, the transcriptional factors AP2 and ARF families were significantly more expressed in the reproductive organs of <em>K. obovata</em> than in those of <em>C. brachiata</em>. At the same time, the ERF family was more expressed in its roots. The findings suggested that the hormone transduction may contribute to viviparous initiation. Transcriptional factors were quite crucial for mangroves' adaptation to wetlands.</p>