TheAUXIN RESPONSE FACTOR 2gene ofArabidopsislinks auxin signalling, cell division, and the size of seeds and other organs

Abstract

Control of seed size involves complex interactions among the zygotic embryo and endosperm, the maternally derived seed coat, and the parent plant. Here we describe a mutant in Arabidopsis, megaintegumenta (mnt), in which seed size and weight are dramatically increased. One factor in this is extra cell division in the integuments surrounding mnt mutant ovules, leading to the formation of enlarged seed coats. Unusually for integument mutants, mnt does not impair female fertility. The mnt lesion also has pleiotropic effects on vegetative and floral development, causing extra cell division and expansion in many organs. mnt was identified as a mutant allele of AUXIN RESPONSE FACTOR 2 (ARF2), a member of a family of transcription factors that mediate gene expression in response to auxin. The mutant phenotype and gene expression studies described here provide evidence that MNT/ARF2 is a repressor of cell division and organ growth. The mutant phenotype also illustrates the importance of growth of the ovule before fertilization in determining final size of the seed.

The Differential Transcription Network between Embryo and Endosperm in the Early Developing Maize Seed

“…[See online article for color version of this figure. ] (GRMZM2G328438), Myb-related (GRMZM2G158117), ARF family (GRMZM5G874163), TCP (GRMZM2G093895), and HB family (GRMZM2G017087, GRMZM2G162481, and GRMZM2G087741), as well as those implicated in hormone signaling pathways, such as B3 domaincontaining factor (Stone et al, 2001), ABI3/VP1 (abscisic acid signaling), ARF and Aux/IAA (auxin signaling; Schruff et al, 2006;Liu et al, 2007;Sreenivasulu et al, 2008;Xing et al, 2011), GRAS (gibberellin signaling), and ARR (cytokinin signaling) homologs. Several TF family members are likely to play a role in cell fate determination, including C2C2-YABBY (GRMZM2G167824 and GRMZM2G529859) and GeBP (GRMZM2G036966) homologs, as well as in cell growth regulation and germination, including WRKY (Zhang et al, 2011a;GRMZM5G816457) and bHLH (GRMZM2G042920) homologs.…”

Endosperm: an integrator of seed growth and development

“…Similarly, reducing the degree of cell elongation in the seed integuments reduces endosperm growth. Conversely, increasing the number of seed integument cells causes a symmetrical increase in endosperm growth [26,27]. In Arabidopsis, the final size of the seed is determined before the embryo initiates the major phase of cell proliferation after the heart embryo stage (Figure 2).…”

Isolation and initial characterization of GW5, a major QTL associated with rice grain width and weight

“…The mutant protein encoded by the da1-1 allele has negative activity toward DA1 and a DA1-related protein, and overexpression of da1-1 cDNA dramatically increases the seed and organ size of wildtype plants [15]. In addition, plant hormones and their receptors [16][17][18][19], as well as the nutritional synthesis pathway [20,21], have also been implicated in the development of grain in crops and other plant species. For example, the rice dwarf11 mutant has a defect in a novel cytochrome P450, which shares homology with enzymes involved in brassinosteroid biosynthesis, and bears seeds of reduced length [17].…”