AUTHOR=Choi Jeongho , Kim Hyojin , Suh Mi Chung 

TITLE=Disruption of the ABA1 encoding zeaxanthin epoxidase caused defective suberin layers in Arabidopsis seed coats

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1156356

DOI=10.3389/fpls.2023.1156356

ISSN=1664-462X

ABSTRACT=<p>Suberin, a complex polyester deposited in the seed coat outer integument, acts as a hydrophobic barrier to control the movement of water, ions, and gas. However, relatively little is known about the signal transduction involved in suberin layer formation during seed coat development. In this study, the effect of the plant hormone abscisic acid (ABA) on suberin layer formation in seed coats was investigated by characterizing mutations in Arabidopsis related to ABA biosynthesis and signaling. Seed coat permeability to tetrazolium salt was noticeably elevated in <italic>aba1-1</italic> and <italic>abi1-1</italic> mutants, but not significantly altered in <italic>snrk2.2/3/6</italic>, <italic>abi3-8</italic>, <italic>abi5-7</italic>, and <italic>pyr1pyl1pyl2pyl4</italic> quadruple mutants compared with that in the wild-type (WT). <italic>ABA1</italic> encodes a zeaxanthin epoxidase that functions in the first step of ABA biosynthesis. <italic>aba1-1</italic> and <italic>aba1-8</italic> mutant seed coats showed reduced autofluorescence under UV light and increased tetrazolium salt permeability relative to WT levels. <italic>ABA1</italic> disruption resulted in decreased total seed coat polyester levels by approximately 3%, with a remarkable reduction in levels of C24:0 ω-hydroxy fatty acids and C24:0 dicarboxylic acids, which are the most abundant aliphatic compounds in seed coat suberin. Consistent with suberin polyester chemical analysis, RT-qPCR analysis showed a significant reduction in transcript levels of <italic>KCS17</italic>, <italic>FAR1</italic>, <italic>FAR4</italic>, <italic>FAR5</italic>, <italic>CYP86A1</italic>, <italic>CYP86B1</italic>, <italic>ASFT</italic>, <italic>GPAT5</italic>, <italic>LTPG1</italic>, <italic>LTPG15</italic>, <italic>ABCG2</italic>, <italic>ABCG6</italic>, <italic>ABCG20</italic>, <italic>ABCG23</italic>, <italic>MYB9</italic>, and <italic>MYB107</italic>, which are involved in suberin accumulation and regulation in developing <italic>aba1-1</italic> and <italic>aba1-8</italic> siliques, as compared with WT levels. Together, seed coat suberization is mediated by ABA and partially processed through canonical ABA signaling.</p>