Molecular Insights into Inflorescence Meristem Specification for Yield Potential in Cereal Crops

Abstract

Flowering plants develop new organs throughout their life cycle. The vegetative shoot apical meristem (SAM) generates leaf whorls, branches and stems, whereas the reproductive SAM, called the inflorescence meristem (IM), forms florets arranged on a stem or an axis. In cereal crops, the inflorescence producing grains from fertilized florets makes the major yield contribution, which is determined by the numbers and structures of branches, spikelets and florets within the inflorescence. The developmental progression largely depends on the activity of IM. The proper regulations of IM size, specification and termination are outcomes of complex interactions between promoting and restricting factors/signals. Here, we focus on recent advances in molecular mechanisms underlying potential pathways of IM identification, maintenance and differentiation in cereal crops, including rice (Oryza sativa), maize (Zea mays), wheat (Triticum aestivum), and barley (Hordeum vulgare), highlighting the researches that have facilitated grain yield by, for example, modifying the number of inflorescence branches. Combinatorial functions of key regulators and crosstalk in IM determinacy and specification are summarized. This review delivers the knowledge to crop breeding applications aiming to the improvements in yield performance and productivity.

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

“…MIKCc genes play an important role in grass inflorescence architecture and spikelet differentiation ( Digel et al, 2015 ; Liu et al, 2015; Li et al, 2021 ; Wang et al, 2021 ). In our study, SVP-like genes, HvMADS22 , HvMADS47 and HvMADS55 , and one A-class gene HvMADS14 ( VRN1 ), and E-class gene HvMADS34 , show a high transcription level at the early inflorescence development stage before spikelet differentiation, suggesting a role for these genes in inflorescence meristem maintenance and spikelet meristem identity.…”

“…The Triticeae crop barley has a simple branchless spike-type inflorescence. During early development, the inflorescence meristem differentiates several spikelet ridges, and each ridge develops a determinate triple spikelet meristem, which in turn gives three spikelet meristems (SM; Wang et al, 2021 ). Each SM produces one floral meristem, always resulting in three single-flowered spikelets per rachis node ( Koppolu and Schnurbusch, 2019 ).…”

Micro-RNA-Regulated SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) Gene Expression and Cytokinin Accumulation Distinguish Early-Developing Male and Female Inflorescences in Oil Palm (Elaeis guineensis)

“…In crop plants, inflorescence structure is an agronomically important character and often affects yield, which depends on the number of flowers available for fertilization. Much research into the determination of inflorescence architecture has focused on cereals due to their great importance to world agriculture and human nutrition [ 1 ], particularly rice and maize [ 2 ], whilst a range of eudicot species such as Arabidopsis thaliana have also been studied [ 3 ].…”

A VIN3-like Protein OsVIL1 Is Involved in Grain Yield and Biomass in Rice

“…To this end, much research has been carried out on increasing rice grain yield. In rice, plant architecture is an important factor that determines productivity, which is well known to depend on meristem activity [ 1 , 2 ]. Cytokinins are important in regulating meristem activity and maintenance by increasing cell division [ 1 , 2 , 3 , 4 , 5 ].…”

“…In rice, plant architecture is an important factor that determines productivity, which is well known to depend on meristem activity [ 1 , 2 ]. Cytokinins are important in regulating meristem activity and maintenance by increasing cell division [ 1 , 2 , 3 , 4 , 5 ]. LONELY GUY ( LOG ) encodes a cytokinin riboside 5′-monophosphate phosphoribohydrolase that functions during the final step in bioactive cytokinin synthesis [ 3 ].…”