Overexpression of Brassica rapa GROWTH-REGULATING FACTOR genes in Arabidopsis thaliana increases organ growth by enhancing cell proliferation

Abstract

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Abstract GROWTH-REGULATING FACTOR (GRF) genes encode plant-specific transcription factors containing two conserved QLQ and WRC domains and play critical roles in regulating the growth and development of lateral organs, such as cotyledons, leaves, and flowers. To explore the agricultural potential of Brassica rapa GRF genes (BrGRFs), the researchers isolated seven BrGRFs (BrGRF3-1, 3-2, 5, 7, 8-1, 8-2, and 9) and constructed BrGRF-overexpressing Arabidopsis thaliana plants (BrGRF-OX). BrGRF-OX plants developed larger cotyledons, leaves, and flowers as well as longer roots than the wild type. The increase in size of these organs were due to increases in cell number, but not due to cell size. BrGRF-OX plants also had larger siliques and seeds. Furthermore, BrGRF-OX seeds produced more oil than the wild type. RT-PCR analysis revealed that BrGRFs regulated expression of a wide range of genes that are involved in gibberellin-, auxin-, cell division-related growth processes. Taken together, the data indicates that BrGRFs act as positive regulators of plant growth, thus raising the possibility that they may serve as a useful genetic source for crop improvement with respect to organ size and seed oil production.

Biological roles and an evolutionary sketch of the GRF-GIF transcriptional complex in plants

“…It has been reported that increases in the GRF activities of Arabidopsis, B. napus , and B. rapa stimulate photosynthetic activities, resulting in an abundance of photosynthetic assimilates or seed oil (21, 41, 42, 59). The increases were concomitant with increases in total chlorophyll content and the rate of chloroplast division (41, 46).…”

Molecular Mechanisms of the miR396b-GRF1 Module Underlying Rooting Regulation in Acer rubrum L.

“…10 To date, GRFs have been shown to promote root growth in transgenic A. thaliana overexpressing GRFs from Brassica rapa, as well as in B. oleracea, rice, and M. truncatula. 10,[36][37][38] Compared to control plants, transgenic B. oleracea rGRF3#10 had greater primary root elongation rates and longer roots. 37 RNAi-mediated inactivation of MtGRF2, MtGRF4, and MtGRF6 in M. truncatula significantly reduced root length and weight, suggesting that MtGRF2, MtGRF4, and MtGRF6 may promote root growth.…”

Genetic regulators of leaf size in Brassica crops

“…The overexpression of BrGRF3-1 / 3–2 / 5 / 7 / 8–1 / 8–2 / 9 in A. thaliana plants increased the size of cotyledons, leaves, flowers, siliques, and seeds, as well as the seed oil content. Furthermore, the enhanced organ growth of the transgenic plants resulted from increased cell proliferation but not cell expansion, indicating that these BrGRFs stimulate organ growth by promoting cell proliferation 61 . In A. thaliana plants, GRF1–4 and GRF7–9 are targeted by miR396, and the expression of miR396 is regulated by TCP4 62 , 63 .…”

“…Rapa BrrTCP2 TCP family Negative Bra012600 AT4G18390 54 B. rapa L. ssp. pekinensis BrGRFs GRF family Positive Bra023066, Bra005268 AT2G36400 61 B. rapa BrNGA1 B3 family Negative Bra097255 AT2G46870 67 B. rapa L. ssp. pekinensis miR319a MicroRNA Positive GenBank ID KJ130320 AT4G23713 73 B. napus miR394 MicroRNA Positive BnaC05g21250D AT1G27340 76 B. napus LCR F-box protein Negative GenBank ID CDX84930.1 AT1G27340 76 B. napus DA1 Ubiquitin-dependent protease Negative BnaC05g14930D AT1G19270 80 B. napus FCA-RRM2 RRM domain Positive BnaC01g21860D AT5G54580 88 B. rapa L. ssp.…”