PT  - JOURNAL ARTICLE
AU  - Ivan Kashkan
AU  - Mónika Hrtyan
AU  - Roberta Filepová
AU  - Zuzana Vondráková
AU  - Jan Hejátko
AU  - Sibu Simon
AU  - Debbie Rombaut
AU  - Thomas B. Jacobs
AU  - Mikko J. Frilander
AU  - Jiří Friml
AU  - Jan Petrášek
AU  - Kamil Růžička
TI  - Mutually opposing activity of PIN7 splicing isoforms is required for auxin-mediated tropic responses in <em>Arabidopsis thaliana</em>
AID  - 10.1101/2020.05.02.074070
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.05.02.074070
4099  - http://biorxiv.org/content/early/2020/05/02/2020.05.02.074070.short
4100  - http://biorxiv.org/content/early/2020/05/02/2020.05.02.074070.full
AB  - Advanced transcriptome sequencing has revealed that the majority of eukaryotic genes undergo alternative splicing (AS). Nonetheless, limited effort has been dedicated to investigating the functional relevance of particular splicing events, even those in the key developmental and hormonal regulators. Here we reveal, in the plant model Arabidopsis thaliana, that the PIN7 gene, which encodes a polarly localized transporter for the phytohormone auxin, produces two evolutionarily conserved transcripts. These isoforms PIN7a and PIN7b, differing in a 4 amino acid motif, are present at nearly equal levels in most cells, except some early developing tissues where the expression of PIN7b is moderately prevalent. Both proteins also transport auxin with similar capacity and directionality. However, only PIN7a but not PIN7b cDNA rescues the phenotypes associated with the pin7 knock-out mutation, consistent with their differences in the subcellular trafficking and dynamics at the plasma membrane. Further phenotypic analyses suggested a joint, mutually opposing activity of both isoforms as being required for correct seedling apical hook formation and auxin-mediated tropic responses. These results establish alternative splicing of the PIN family as an evolutionary conserved, functionally relevant mechanism, taking part in the auxin-mediated plant development.Competing Interest StatementThe authors have declared no competing interest.