Regulation of spikelet number during wheat spike development

Area of Science:

• Plant Science
• Agricultural Science
• Genetics

Background:

• Wheat inflorescences (spikes) are composed of spikelets, and the spikelet number per spike (SNS) is a critical determinant of grain yield.
• Spikelet development is initiated by the transition of the shoot apical meristem to an inflorescence meristem (IM), which generates lateral spikelet meristems (SMs).

Purpose of the Study:

• This review focuses on the gene networks that regulate spikelet development and influence the final SNS in wheat.
• To understand how meristem identity genes, florigen transport, and meristem transitions contribute to SNS.

Main Methods:

• Review of existing literature on wheat spike and spikelet development.
• Analysis of genetic factors influencing meristem identity and florigen signaling.
• Exploration of recent advancements in spatial transcriptomics, single-cell analyses, and multi-omics studies.

Main Results:

• The final SNS is determined by the rate of SM production and the timing of the IM to terminal spikelet (IM→TS) transition.
• Genes in the IM and the transport of FLOWERING LOCUS T1 (florigen) from leaves significantly regulate SNS.
• Mutations causing SM-to-IM reversion can lead to supernumerary spikelets (SS) or branches, though with potential trade-offs in fertility and grain weight.

Conclusions:

• Identifying and deploying gene combinations that increase SNS without negatively impacting other yield components is a key breeding strategy.
• Advanced molecular techniques are accelerating the discovery of novel genes and enhancing the potential for engineering more productive wheat spikes.
• Further research is needed to overcome trade-offs associated with certain mutations to fully leverage their potential in commercial wheat varieties.