Intra-Kernel Reallocation of Proteins in Maize Depends on VP1-Mediated Scutellum Development and Nutrient Assimilation

Abstract

During maize (Zea mays) seed development, the endosperm functions as the major organ for storage of photoassimilate, serving to nourish the embryo. a-Zeins and globulins (GLBs) predominantly accumulate in the maize endosperm and embryo, respectively. Here, we show that suppression of a-zeins by RNA interference (aRNAi) in the endosperm results in more GLB1 being synthesized in the embryo, thereby markedly increasing the size and number of protein storage vacuoles. Glb genes are strongly expressed in the middle-to-upper section of the scutellum, cells of which are significantly enlarged by aRNAi induction. Elimination of GLBs caused an apparent reduction in embryo protein level, regardless of whether a-zeins were expressed or suppressed in the endosperm, indicating that GLBs represent the dominant capacity for storage of amino acids allocated from the endosperm. It appears that protein reallocation is mostly regulated at the transcriptional level. Genes differentially expressed between wild-type and aRNAi kernels are mainly involved in sulfur assimilation and nutrient metabolism, and many are transactivated by VIVIPAROUS1 (VP1). In vp1 embryos, misshapen scutellum cells contain notably less cellular content and are unable to respond to aRNAi induction. Our results demonstrate that VP1 is essential for scutellum development and protein reallocation from the endosperm to embryo.

Carotenoids modulate kernel texture in maize by influencing amyloplast envelope integrity

“…For analysis of zeins in immature kernels, endosperms were collected at 18 and 24 DAP, and ground in the lipid nitrogen into fine powder. The extraction and analysis of zein proteins was according to the standard method of our laboratory 42 . For assaying the total protein content, 60 mg of endosperm powder was used for measurement by the instrument of ELEMENTAR Rapid N exceed.…”

“…The nonzein protein extraction was according to the standard method of our laboratory 42 . Twenty μg of nonzein proteins were used for immunoblotting analysis following the manufacture’s protocol, (Bio-Rad, catalog number 162-0177).…”

Integrative hormone and transcriptome analyses underline the role of abscisic acid in seed shattering of weedy rice

“…OsVP1, a global regulator in the integrated seed maturation and germination developmental program, mediated the ABA response during mid-to late-phase embryogenesis [26][27][28]. Thus we performed immunoblot analysis and found that there was no signi cant difference in VP1 protein content at different stages of seed development between WR04-6 and SN9816 ( Fig.…”

Embryo-Endosperm Interaction and Its Agronomic Relevance to Rice Quality

“…② CDC2A (Nowack et al, 2006). ③ VP1 (Zheng et al, 2019). (D) Developmental coordination between embryo and endosperm.…”

“…of endosperm through endosperm-embryo communication, likely the ABA signaling pathway. It regulates scutellum development, enlarges embryo nutrient-storage capacity, and consequently mediates nutrient remobilization from endosperm to embryo (Zheng et al, 2019).…”