Functional retrogression of LOFSEPs in specifying floral organs in barley

This study is led by Professor Matthew R. Tucker (Waite Research Institute, School of Agriculture, Food and Wine, The University of Adelaide) and Professor Gang Li (Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University). The authors created and studied all single, double, and triple mutants for the barley LOFSEP clade in an attempt to overcome expected genetic redundancy. Surprisingly, loss of function of all LOFSEP members only disturbs lemma development, either converting this hull organ into a leaf-like structure or reducing its size. The inner organs including lodicules, anthers and pistil remain unaffected.

A systematic interrogation of how ABCDE class genes are affected in all whorls of the mutants was undertaken. Generally, in the lemma and palea of lofsep mutants, A- and E-class genes are hyperactivated, B- and C- classes are slightly repressed, and D-class genes show unchanged expression in inner organs. The analysis of inner floral organs indicates a functional regression of LOFSEP members in regulating inner organ development, which may be partly attributed to the distinct regulation within barley LOFSEP and floral homeotic genes compared to rice.

In contrast, knockout mutants of HvMADS6, an AGL6 member closely related to the E-class genes, exhibited severe changes in floral organ patterning, leading to the transformation of palea, lodicules, and stamens into lemma-like organs and the formation of new spikelets. These findings provide evidence for functional retrogression of LOFSEPs in specifying floral organs in barley, with MADS6 appearing as a potential substitute for this role compared to rice. Thus, diverged evolutionary strategies involving MADS-box genes appear to have been recruited into in two major modern crops.

See the article:

Functional Retrogression of LOFSEPs in Specifying Floral Organs in Barley

https://link.springer.com/article/10.1007/s42994-024-00182-4