More cuttings
One of the magical characteristics of plants is the ability to grow new plants from cuttings. Think about it, a whole new plant from a tiny piece of another plant. Some plants use it as a way for asexual reproduction. While other plants need some help, only then they will start growing new roots and shoots. Now Japanese researchers have discovered what limits the numbers of new shoots.
For cuttings that can use some extra support it is known that they need a little extra of the phytohormone auxin to get the cell division started. Followed by some extra cytokinin to develop new growth centres. For this cytokinin turns on growth centre master regulator WUS. But this only occurs in a few cells. The question is what prevents the switch on of WUS in those other cells.
The researchers set out to find the answer to this. They got a hint from an earlier study that showed that WOX13 was needed for tissue repair. Analysing the effect of WOX13 on cuttings the researchers studied cuttings with and without WOX13. It turned out that cuttings without WOX13 developed more shoots.
But is WOX13 not there, then WUS is taking its chance
Zooming in on WOX13 and when it is active, the researchers noticed that WOX13 is turned on during the first phase, when the cell divisions were started up. While during the second phase, the formation of the growth centres, WOX13 slowly disappeared from the future growth centre. Moreover, the researchers noticed more activity of WUS and other growth centre genes in cuttings without WOX13.
Remarkable, it turned out that cells which have WOX13 turned on, WUS is turned off. This, so discovered the researchers, was the result of WOX13 actively turning off WUS. In addition, WOX13 also turned off other genes needed for the growth centre development. In turn, WUS turns of WOX13. Allowing the development of small groups were WUS and other growth centre genes are turned on, from here new shoots grow. While the cells with WOX13 turned on matured more quickly.
Because WOX13 turns off WUS, it prevents too many cells from developing into growth centres. In this way cuttings only grow a limiting number of new shoots. But is WOX13 not there, then WUS is taking its chance and develops more growth centres, and more shoots.
Literature
Nao Ogura, Yohei Sasagawa, Tasuku Ito, Toshiaki Tameshige, Satomi Kawai, Masaki Sano, Yuki Doll, Akira Iwase, Ayako Kawamura, Takamasa Suzuki, Itoshi Nikaido, Keiko Sugimoto, and Momoko Ikeuchi (2023) WUSCHEL-RELATED HOMEOBOX 13 suppresses de novo shoot regeneration via cell fate control of pluripotent callus. Sci. Adv.9, eadg6983 DOI: 10.1126/sciadv.adg6983
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