Only Two Genes Make The Difference Between Herbaceous Plants And Trees

Scientists from VIB at Ghent University have succeeded in converting annual plants into perennials. They discovered that the deactivation of two genes in annuals led to the formation of structures that converted the plant into a perennial. This was most likely an important mechanism in plant evolution, initiating the formation of trees.


Annuals and perennials


Annual crops grow, blossom and die within one year. Perennials overwinter and grow again the following year. The life strategy of many annuals consists of rapid growth following germination and rapid transition to flower and seed formation, thus preventing the loss of energy needed to create permanent structures. They germinate quickly after the winter so that they come out before other plants, thus eliminating the need to compete for food and light. The trick is basically to make as many seeds as possible in as short a time as possible.


Perennials have more evolved life strategies for surviving in poor conditions. They compose perennial structures such as overwintering buds, bulbs or tubers. These structures contain groups with cells that are not yet specialised, but which can later be converted when required into new organs such as stalks and leaves.


The flowering of annuals


Annual crops consume all the non-specialised cells in developing their flowers. Thus the appearance of the flower signals means the end of the plant. But fortunately they have left seeds that sense - after winter - that the moment has come to start up. Plants are able to register the lengthening of the days. With the advent of longer days in the spring, a signal is sent from the leaves to the growth tops to activate a limited number of blooming-induction genes.


Deactivating two genes


VIB researchers, such as Siegbert Melzer in Tom Beeckman's group, have studied two such flower-inducing genes. They have deactivated them in thale cress (Arabidopsis thaliana), a typical annual. The VIB researchers found that mutant plants can no longer induce flowering, but they can continue to grow vegetatively or come into flower much later. Melzer had found that modified crops did not use up their store of non-specialised cells, enabling perennial growth. They can therefore continue to grow for a very long time.


As with real perennials these plants show secondary growth with wood formation creating shrub-like Arabidopsis plants.



Raising the veil of evolution


Researchers have been fascinated for a long time by the evolution of herbaceous to woody structures. This research clearly shows only two genes are in fact necessary in this process. This has probably been going on throughout the evolution of plants. Furthermore it is not inconceivable this happened independently on multiple occasions.


Relevant scientific publication


The research appears in the leading journal Nature Genetics (Siegbert Melzer et al., Flowering-time genes modulate meristem determinacy and growth form in Arabidopsis thaliana).















Funding


This research was financed by VIB, UGent, IWT, FWO.


Tom Beeckman is in charge of the Root Development research group in the VIB Plant Systems Biology department, UGent - under the management of Dirk InzГ©. Click here for more information.


VIB is a non-profit research institute in life sciences. Approximately 1100 scientists and technicians perform basic research into the molecular mechanisms that are responsible for the functioning of the human body, plants and micro-organisms. By means of a strong partnership with four Flemish universities - UGent, K.U.Leuven, Universiteit Antwerpen and Vrije Universiteit Brussel - and a robust investment programme, VIB bundles the strengths of 65 research groups into one institute. Their research aims at fundamentally pushing out the boundaries of our knowledge. With its technology transfer activities VIB aims to convert research results into products for the consumer and the patient. VIB develops and disseminates a broad range of scientifically based information on all aspects of biotechnology. More information on vib.be.


The Universiteit Gent (UGent) is one of the largest Dutch-speaking universities, with more than 30,000 students. The course options include almost all academic courses that are offered in Flanders.
The UGent prides itself on being an open, socially engaged and pluralistic university with an international perspective. More information on ugent.be.

Universiteit Gent