Integrated physiological and transcriptomic measurements reveal changes in the accumulation and partitioning of storage reserves after prevention of pollination in maize.

BACKGROUND

Reduced sink demand, such as that caused by grain or ear removal, is known to accelerate senescence in maize; nonetheless, how diminished sink strength mechanistically triggers senescence and disrupts grain development remains poorly understood. In particular, the transcriptional and metabolic regulatory networks that link reduced sink demand to the onset of senescence have not been clearly defined.

RESULTS

We grew the maize inbred line 08LF, which exhibits early senescence in response to grain removal, under non-pollinated (NONPOL) and normally pollinated (POL) conditions. We then collected phenotypic, physiological, and transcriptomic data from developing grains (6 to 24 days after silking) to gain insight into the molecular mechanisms responsible for the changes induced under NONPOL conditions. Pollination prevention induced early senescence, and major transcriptomic divergence between POL and NONPOL grains occurred between 14 and 18 DAS, indicating a key time window associated with the onset of senescence under reduced sink demand. Key pathways involved in starch, sucrose, and trehalose metabolism were disrupted in nonpollinated grains, and gene co-expression network analysis identified five co-expressed modules linked to energy metabolism, photosynthesis, and stress responses. These modules were correlated with changes in sugar accumulation and oxidative stress indices. Importantly, 20 hub genes, including genes encoding MYB transcription factors and heat shock proteins, were identified as potential regulators of the senescence process triggered by reduced sink demand. These genes may represent key components for dissecting the regulatory mechanisms that underlie senescence triggered by reduced sink demand in maize.

CONCLUSIONS

This study links reduced sink demand to coordinated metabolic and transcriptional changes associated with senescence, providing novel insights and genetic resources for understanding maize grain development under stress.