Biosynthesis‐ and transport‐mediated dynamic auxin distribution during seed development controls seed size in Arabidopsis

Abstract

SUMMARY Auxin is indispensable to the fertilization‐induced coordinated development of the embryo, endosperm, and seed coat. However, little attention has been given to the distribution pattern, maintenance mechanism, and function of auxin throughout the process of seed development. In the present study, we found that auxin response signals display a dynamic distribution pattern during Arabidopsis seed development. Shortly after fertilization, strong auxin response signals were observed at the funiculus, chalaza, and micropylar integument where the embryo attaches. Later, additional signals appeared at the middle layer of the inner integument (ii1′) above the chalaza and the whole inner layer of the outer integument (oi1). These signals peaked when the seed was mature, then declined upon desiccation and disappeared in the dried seed. Auxin biosynthesis genes, including ASB1, TAA1, YUC1, YUC4, YUC8, and YUC9, contributed to the accumulation of auxin in the funiculus and seed coat. Auxin efflux carrier PIN3 and influx carrier AUX1 also contributed to the polar auxin distribution in the seed coat. PIN3 was expressed in the ii1 (innermost layer of the inner integument) and oi1 layers of the integument and showed polar localization. AUX1 was expressed in both layers of the outer integument and the endosperm and displayed a uniform localization. Further research demonstrated that the accumulation of auxin in the seed coat regulates seed size. Transgenic plants that specifically express the YUC8 gene in the oi2 or ii1 seed coat produced larger seeds. These results provide useful tools for cultivating high‐yielding crops.

Insight into regulation of adventitious root formation by arbuscular mycorrhizal fungus and exogenous auxin in tea plant (Camellia sinensis L.) cuttings

“…Auxin in higher plants can be transported in two ways, long-distance vascular transport and short-distance active transport, also known as auxin polar transport ( Li and Li, 2019 ). The latter plays a key role in the asymmetric distribution of auxin and requires transport carriers, which mainly include AUX/LAX family proteins (auxin influx carriers), PIN (PIN-FORMED) family proteins (auxin efflux carriers), and ABCB/MDR/PGP family proteins with both influx and efflux functions ( Cho and Cho, 2013 ; Liu et al., 2023b ). Plants generally fulfil the polar transport and distribution of auxin by regulating these family proteins.…”

Characterization of the PIN Auxin Efflux Carrier Gene Family and Its Expression during Zygotic Embryogenesis in Persea americana

“…Auxin, in its most abundant form IAA, is perhaps the molecule involved in almost all aspects of plant life [ 69 , 73 ]. In particular, IAA is vital for the coordinated development of all phases of somatic embryos [ 74 , 75 , 76 , 77 ]. IAA requires local biosynthesis [ 78 ] and PAT from cell to cell [ 15 , 79 ] to perform its function.…”

Dormancy heterogeneity among Arabidopsis thaliana seeds is linked to individual seed size

“…Moreover, both Arabidopsis seed shape and size are affected by mutations in multiple genes involved in diverse developmental and hormonal pathways (reviewed in Orozco-Arroyo et al., 2015 ; Li and Li, 2016 ). These include genes implicated in responses to hormones such as abscisic acid (ABA) ( Xi et al., 2010 ), auxin ( Liu et al., 2023 ), cytokinins ( Riefler et al., 2005 ; Liu et al., 2020 ), brassinosteroids ( Jiang et al., 2013 ), and ethylene ( Robert et al., 2008 ), as well as genes that directly regulate seed development ( Leon-Kloosterziel et al., 1994 ; Garcia et al., 2003 ; Robert et al., 2008 ; Zhou et al., 2009 ; Doughty et al., 2014 ; Cheng et al., 2018 ; Yu et al., 2023 ). Finally, Arabidopsis seed size is also affected by allocation of storage materials during seed maturation ( Herridge et al., 2011 ; Li et al., 2022 ).…”