Arabidopsis MDN1 Is Involved in the Establishment of a Normal Seed Proteome and Seed Germination.

Peng-Cheng Li,Guang-Hui Li,Xing-Jun Wang,Xi-Meng Zhou,Chuan-Zhi Zhao,Jun-Jie Ma,Shou-Jin Fan,Han Xia

doi:10.3389/fpls.2019.01118

Abstract

Seed germination and formation are the beginning and ending, respectively, of a plant life cycle. These two processes are under fine regulation by the internal genetic information. Previously, we demonstrated that Arabidopsis MIDASIN 1 (MDN1) is required for ribosome biogenesis, and its dysfunction leads to pleiotropic developmental phenotypes, including impaired embryogenesis and slow seed germination. In this study, we further found that the weak mutant of MDN1, mdn1-1, exhibits an increased seed size phenotype. Seed proteomic analysis reveals that a number of proteins involved in seed development and response to external environments are mis-regulated by the MDN1 dysfunction. Many 2S seed storage proteins (SSPs) and late embryogenesis abundant (LEA) proteins are over-accumulated in the dry seeds of mdn1-1. Further, some genes encoding seed storage reserves are also upregulated in mdn1-1 seedlings. More interestingly, abscisic acid-insensitive 5 (ABI5) is over-accumulated in mdn1-1 seeds, and the loss of its function partially rescues the low seed germination rate of mdn1-1. Together, this study further demonstrates that MDN1 is essential for establishing a normal seed proteome, and its mutation triggers ABI5-mediated repression of seed germination.

Highlights

The seed is an important organ for plant species dispersion (Rodriguez-Gacio Mdel et al, 2009)
MIDASIN 1 (MDN1) dysfunction in mdn1-1 leads to the ribosomal stress response given its essential roles in nuclear export of the pre60S ribosomal particle and maturation of pre-rRNAs (Li et al, 2019)
Ribosomal stress is concomitant with multiple developmental defects throughout the plant life cycle, including impaired embryogenesis, pointed and narrow leaves, retarded root growth, altered flowering time, and reduced fertility (Byrne, 2009; Weis et al, 2015a)

Summary

INTRODUCTION

The seed is an important organ for plant species dispersion (Rodriguez-Gacio Mdel et al, 2009). The storage compounds required for germination, including lipids, carbohydrates, and proteins, accumulate in the embryo, the endosperm, or the aleurone layer depending on the species At this stage, the embryo becomes quiescent and desiccation-tolerant. ABI3 is a B3-domain transcription factor involved in seed maturation (Kroj et al, 2003), and its gene is expressed in developing and germinating seeds (Baumbusch et al, 2004; Bassel et al, 2006). ABI5 is required for the expression of some LEA protein genes (Finkelstein and Lynch, 2000), and the abi mutant displays a large-seed phenotype (Cheng et al, 2014), suggesting that ABI5 is involved in seed maturation. We further found that mdn has larger seeds than wild type, and the low germination rate of its seeds is mediated by ABI5 to some extent

MATERIALS AND METHODS

RESULTS

Findings

DISCUSSION