Incomplete filling in the basal region of maize endosperm: timing of development of starch synthesis and cell vitality

• Published in: The Plant journal : for cell and molecular biology Vol. 120; no. 3; pp. 1142 - 1158
• Main Authors: Chen, Xian‐Min, Wang, Zhi‐Wei, Liang, Xiao‐Gui, Li, Feng‐Yuan, Li, Bin‐Bin, Wu, Gong, Yi, Fei, Setter, Tim L., Shen, Si, Zhou, Shun‐Li
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.11.2024
• Subjects: Abscisic acid; Accumulation; basipetal starch accumulation; cell vitality; Corn; Developmental stages; Endosperm; Gene expression; Genetic analysis; hormone signaling; maize endosperm; Nonuniformity; Pattern analysis; physiological development index; Physiology; Signal transduction; Starch; Synthesis; T6P/SnRK1 signaling; Transcriptomes; Trehalose; maize endosperm; hormone signaling; T6P/SnRK1 signaling; basipetal starch accumulation; cell vitality; physiological development index
• ISSN: 0960-7412; 1365-313X; 1365-313X
• DOI: 10.1111/tpj.17043

SUMMARY Starch synthesis in maize endosperm adheres to the basipetal sequence from the apex downwards. However, the mechanism underlying nonuniformity among regions of the endosperm in starch accumulation and its significance is poorly understood. Here, we examined the spatiotemporal transcriptomes and starch accumulation dynamics in apical (AE), middle (ME), and basal (BE) regions of endosperm throughout the filling stage. Results demonstrated that the BE had lower levels of gene transcripts and enzymes facilitating starch synthesis, corresponding to incomplete starch storage at maturity, compared with AE and ME. Contrarily, the BE showed abundant gene expression for genetic processing and slow progress in physiological development (quantified by an index calculated from the expression values of development progress marker genes), revealing a sustained cell vitality of the BE. Further analysis demonstrated a significant parabolic correlation between starch synthesis and physiological development. An in‐depth examination showed that the BE had more active signaling pathways of IAA and ABA than the AE throughout the filling stage, while ethylene showed the opposite pattern. Besides, SNF1‐related protein kinase1 (SnRK1) activity, a regulator for starch synthesis modulated by trehalose‐6‐phosphate (T6P) signaling, was kept at a lower level in the BE than the AE and ME, corresponding to the distinct gene expression in the T6P pathway in starch synthesis regulation. Collectively, the findings support an improved understanding of the timing of starch synthesis and cell vitality in regions of the endosperm during development, and potential regulation from hormone signaling and T6P/SnRK1 signaling. Significance Statement Spatiotemporal transcriptome and starch synthesis dynamics during development revealed the timing of starch accumulation and cell vitality in regions of the maize endosperm and its regulations by T6P/SnRK1 and hormone signals. The finding supports an improved understanding of the nonuniformities of starch accumulation and cell vitality in maize endosperm.