Transcript Profiling of MIKCc MADS-Box Genes Reveals Conserved and Novel Roles in Barley Inflorescence Development

Hendrik N J Kuijer; Neil J Shirley; Shi F Khor; Jin Shi; Julian Schwerdt; Dabing Zhang; Gang Li; Rachel A Burton

doi:10.3389/fpls.2021.705286

Transcript Profiling of MIKCc MADS-Box Genes Reveals Conserved and Novel Roles in Barley Inflorescence Development

Front Plant Sci. 2021 Sep 1:12:705286. doi: 10.3389/fpls.2021.705286. eCollection 2021.

Authors

Hendrik N J Kuijer¹, Neil J Shirley¹, Shi F Khor¹, Jin Shi², Julian Schwerdt¹, Dabing Zhang^{1

2}, Gang Li^{1

3}, Rachel A Burton¹

Affiliations

¹ School of Agriculture Food and Wine, University of Adelaide, Glen Osmond, SA, Australia.
² Joint International Research Laboratory of Metabolic and Developmental Sciences, Shanghai Jiao Tong University-University of Adelaide Joint Centre for Agriculture and Health, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
³ School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, China.

Abstract

MADS-box genes have a wide range of functions in plant reproductive development and grain production. The ABCDE model of floral organ development shows that MADS-box genes are central players in these events in dicotyledonous plants but the applicability of this model remains largely unknown in many grass crops. Here, we show that transcript analysis of all MIKCc MADS-box genes through barley (Hordeum vulgare L.) inflorescence development reveals co-expression groups that can be linked to developmental events. Thirty-four MIKCc MADS-box genes were identified in the barley genome and single-nucleotide polymorphism (SNP) scanning of 22,626 barley varieties revealed that the natural variation in the coding regions of these genes is low and the sequences have been extremely conserved during barley domestication. More detailed transcript analysis showed that MADS-box genes are generally expressed at key inflorescence developmental phases and across various floral organs in barley, as predicted by the ABCDE model. However, expression patterns of some MADS genes, for example HvMADS58 (AGAMOUS subfamily) and HvMADS34 (SEPALLATA subfamily), clearly deviate from predicted patterns. This places them outside the scope of the classical ABCDE model of floral development and demonstrates that the central tenet of antagonism between A- and C-class gene expression in the ABC model of other plants does not occur in barley. Co-expression across three correlation sets showed that specifically grouped members of the barley MIKCc MADS-box genes are likely to be involved in developmental events driving inflorescence meristem initiation, floral meristem identity and floral organ determination. Based on these observations, we propose a potential floral ABCDE working model in barley, where the classic model is generally upheld, but that also provides new insights into the role of MIKCc MADS-box genes in the developing barley inflorescence.

Keywords: ABC model; MADS; barley; floral organs; floret; inflorescence; meristems; transcript profiling.