Roles of BdUNICULME4 and BdLAXATUM-A in the non-domesticated grass

Kévin Magne, Shengbin Liu, Sophie Massot, Marion Dalmais, Halima Morin, Richard Sibout, Abdelhafid Bendahmane and Pascal Ratet

The team of P. Ratet (Université Paris-Saclay, CNRS, INRAE, Univ Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91405, Orsay, France) is exploring the roles of the NOOT-BOP-COCH-LIKE (NBCL) genes in plant development. They previously described the role of NBCL genes in the regulation of symbiotic nodule identity in Medicago, pea and lotus (Plant Cell; The Plant Journal) and in the regulation of aerial organ abscission in legume plants (New Phytologist). The study of NBCL genes in grasses such as barley, maize and rice revealed that NBCLs positively contribute to agronomic traits influencing yield, such as tillering, leaf proximal-distal patterning and floral organ identity. However, our understanding of the roles of the NBCL genes in grass species remained incomplete as these studies were restricted to domesticated crops which have been subjected to selection events that might have occulted some gene functions.

In this new study, the team of P. Ratet characterized the NBCL genes BdUNICULME4 (CUL4) and BdLAXATUM-A (LAXA) in the non-domesticated grass species Brachypodium distachyon (The Plant Journal). They used Targeted Induced Local Lesions IN Genome (TILLING) mutants and showed that CUL4 was required for leaf patterning, especially for the development of the ligule and auricles. CUL4 was also involved in secondary tillering and in the control of the inflorescence meristematic activity. They also showed that LAXA contributed negatively to secondary tillering but positively to the development of the spikelets, and more specifically in spikelet architecture relaxation. In addition, they showed that LAXA contributed to the control of the number and identity of floral organs.

By using the non-domesticated species, Brachypodium distachyon, this work thus highlights new roles for NBCL genes in grass development.

Figure legend: The main phenotypes of Brachypodium distachyon nbcl mutants. The loss-of-function of B. distachyon NBCL genes impacts the tillering (a-c), the patterning of the blade-sheath boundary region (d-f), as well as the spikelet architecture (g-i) and the floral organ identity (j-l). Wild type (a,d,g,j), cul4 (b,e,h,k) and laxa (c,f,i,l).

Contact: pascal.ratet @ cnrs.fr