Seed dispersal is an essential trait that enables colonization of new favorable habitats, ensuring species survival. In plants with dehiscent fruits, such as Arabidopsis, seed dispersal depends on two processes: the separation of the fruit valves that protect the seeds (fruit dehiscence) and the detachment of the seeds from the funiculus connecting them to the mother plant (seed abscission). The key factors required to establish a proper lignin pattern for fruit dehiscence are SHATTERPROOF 1 and 2 (SHP1 and SHP2). Here, we demonstrate that the SHP-related gene SEEDSTICK (STK) is a key factor required to establish the proper lignin pattern in the seed abscission zone but in an opposite way. We show that STK acts as a repressor of lignin deposition in the seed abscission zone through the direct repression of HECATE3, whereas the SHP proteins promote lignin deposition in the valve margins by activating INDEHISCENT. The interaction of STK with the SEUSS co-repressor determines the difference in the way STK and SHP proteins control the lignification patterns. Despite this difference in the molecular control of lignification during seed abscission and fruit dehiscence, we show that the genetic networks regulating these two developmental pathways are highly conserved.
The authors declare no competing or financial interests.
V.B. and I.R.-V. designed, performed and interpreted experiments and wrote the paper, S.M. and M.D.M. performed and interpreted experiments and L.C. interpreted experiments and wrote the paper.
This work was supported by the Fondazione Cariplo [2009-2990 to V.B. and 2011-2257 to S.M.]; and the Ministry of Education, Universities and Research, Italy (Ministero dell'Istruzione, dell'Università e della Ricerca) [FIRB RBFR08UG7 to I.R.-V.].
Sequence data from this article can be found in the Arabidopsis Genome Initiative or GenBank/EMBL databases under the following accession numbers: ALC (At5g67110), HEC3 (At5g09750), IND (At4g00120), LUG (At4g32551), SEP3 (At1g24260), SEU (At1g43850), SHP1 (At3g58780), SHP2 (At2g42830), SPT (At4g36930), STK (At4g09960).
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.135202.supplemental
- Received January 14, 2016.
- Accepted August 2, 2016.