MYB56 Encoding a R2R3 MYB Transcription Factor Regulates Seed Size in Arabidopsis thaliana

Abstract

Plant seed size is tightly regulated by the development of seed coat, embryo, and endosperm; however, currently, its underlying mechanism remains unclear. In this study, we revealed a regulatory role of an R2R3 MYB transcription factor MYB56 in controlling seed size specifically in Arabidopsis thaliana L. Loss-of-function or knock-down of MYB56 yielded smaller seeds as compared with the wild type. Conversely, overexpression of MYB56 produced larger seeds. Further observation using semi-thin sections showed that myb56 developed smaller contracted endothelial cells and reduced cell number in the outer integument layer of the seed coat during the seed development; by contrast, MYB56 overexpressing lines had expanded endothelial cells and increased cell number in the outer integument layer of the seed coat, suggesting the essential role of MYB56 in regulating seed development. In addition, reciprocal cross-analysis showed that MYB56 affected the seed development maternally. MYB56 was shown to be dominantly expressed in developing seeds, consistently with its function in seed development. Moreover, quantitative reverse transcription polymerase chain reaction analysis revealed that MYB56 regulates the expression of genes involved in cell wall metabolism such as cell division and expansion. Altogether, our results demonstrated that MYB56 represents an unknown pathway for positively controlling the seed size.

Inference of the Arabidopsis Lateral Root Gene Regulatory Network Suggests a Bifurcation Mechanism That Defines Primordia Flanking and Central Zones

“…The new network topology contained a single very long genetic cascade featuring ARF7 at the top and meristematic and patterning genes at the bottom ( Figure 6A). The "full cascade" topology is supported by the observations that (1) MP and PLT3 are now located several steps downstream of ARF7 Hofhuis et al, 2013), and (2) the MYB56 gene, one of the predicted links, has recently been shown to control seed size by regulating cell division in the integument of the seed coat, exactly as ANT, its predicted target (Mizukami and Fischer, 2000;Zhang et al, 2013). Interestingly, at the very top of the cascade, the gravistimulus is predicted by TDCor to trigger a nontranscriptional response leading to posttranslational activation of the ARF7 protein ( Figures 4A and 6A).…”

Networks controlling seed size in Arabidopsis

“…In 477 the ttg2 mutant, cell elongation in the integuments is 478 affected, possibly because of the increased physical con-479 straint of the cell walls, or possibly because of disruption of 480 the developmental pathways for elongation. Endosperm 481 development is also affected, probably as a consequence of 482 the defects in integument cells (Garcia et al 2003(Garcia et al , 2005 (Zhang et al 2013). The loss-of-function 510 mutant lines of MYB56 generate smaller seeds, while 511 overexpression of MYB56 generates larger seeds compared 512 with wild type.…”

“…myb56 endothelial cells are smaller and 513 more rounded. Apparently, the role of MYB56 is locally 514 dependent since its altered expression on the endothelial 515 layer affects cell size but not cell number; however, in the 516 two layers of the outer integument, MYB56 controls only 517 cell number but not the cell size (Zhang et al 2013). 518 MYB56 affects seed size in a regulatory pathway probably 519 independent of other seed coat development regulators 520 such as TTG2, KLU, GORDITA (GOA) and DA1, because 521 these genes show no expression changes in a myb56 mutant 522 background (Zhang et al 2013).…”

“…Apparently, the role of MYB56 is locally 514 dependent since its altered expression on the endothelial 515 layer affects cell size but not cell number; however, in the 516 two layers of the outer integument, MYB56 controls only 517 cell number but not the cell size (Zhang et al 2013). 518 MYB56 affects seed size in a regulatory pathway probably 519 independent of other seed coat development regulators 520 such as TTG2, KLU, GORDITA (GOA) and DA1, because 521 these genes show no expression changes in a myb56 mutant 522 background (Zhang et al 2013). 523 SEEDSTICK (STK) and Arabidopsis B-sister (ABS) are 524 two MADS-box genes that act together to control the for-525 mation of one layer of the seed coat, the endothelium, 526 during seed development (Mizzotti et al 2012).…”

Two ATP Binding Cassette G (ABCG) Transporters, OsABCG26 and OsABCG15, Collaboratively Regulate Rice Male Reproduction

“…qRT-PCR procedures and data analysis were performed as previous described (Li et al, 2006;Zhang et al, 2013). All of the primers used for qRT-PCR are listed in Supplemental Table S3.…”