A Novel Function of Abscisic Acid in the Regulation of Rice (Oryza sativa L.) Root Growth and Development

Abstract

Plant roots retain developmental plasticity and respond to environmental stresses or exogenous plant growth regulators by undergoing profound morphological and physiological alteration. In this study, we investigated the effects of exogenous ABA on root growth and development in Taichung native 1 (TN1) rice. Exogenous application of 10 microM ABA leads to swelling, root hair formation and initiation of lateral root primodia in the tips of young, seminal rice roots. Cortex cells increased in size and were irregularly shaped. ABA treatment significantly increased 2, 3, 5-triphenyl tetrazolium chloride (TTC) reductase ability in the root tips and the exudation rate of xylem sap. In addition, the K(+) ion content in xylem sap increased nearly 2-fold, but not that of Ca(2+) or Mg(2+). Analysis of proteins expressed in the root tips identified several ABA-induced or -repressed proteins, including actin depolymerization factor (ADF), late embryo abundant protein (LEA), putative steroid membrane-binding protein, ferredoxin thionine reductase and calcium-binding protein. The effects of ABA on root morphogenesis change were Ca(2+) dependent and required the participation of calmodulin and de novo protein synthesis. A model is presented that illustrates how ABA acts through a potential cellular and signal transduction mechanism to induce morphological and physiological changes in rice roots.

Abscisic Acid- and Stress-Induced Highly Proline-Rich Glycoproteins Regulate Root Growth in Rice

“…It is important to note that shorter roots are the consequence of reduced growth rate in the elongation zone rather than in the cell division zone (Sharp et al, 2004;Yamaguchi et al, 2010). We have observed that ABA treatment also leads to shorter and more branched roots, which is consistent with previously published work (Chen et al, 2006). Our findings that ABA treatment restricts RePRP expression in the root elongation zone and not in the division zone suggest that RePRPs may be responsible for the inhibitory effect of ABA/stress on root elongation.…”

“…In addition, the root length increase of the maize (Zea mays) vp mutant was significantly lower than that in the wild type under water deficit conditions, indicating that ABA is required for maintaining rather than completely repressing root development under water stress (Sharp, 2002;Sharp and LeNoble, 2002). The effects of ABA application on rice root have been observed to include the swelling of young root tips, abundant formation of root hairs, and initiation of lateral roots close to tips (Chen et al, 2006). These morphological changes require the involvement of calmodulin and de novo protein synthesis, but the mechanism is still unclear.…”

Effect of exogenous abscisic acid on the level of antioxidants in Atractylodes macrocephala Koidz under lead stress

“…ABA inhibited shoot growth and had no effect on root growth with an increase of lateral root number in the absence of Pb, whereas 10 mg L −1 ABA treatment promoted root and inhibited shoot growth. Previous studies have shown that exogenous ABA usually inhibits shoot growth, but maintains or even promotes root growth when applied to nonstressed rice (Chen et al 2006) and Cynanchum komarovii (Yang et al 2007) seedlings, but a few studies report that exogenous ABA can increase shoot growth. The stimulatory effects of ABA on shoot growth might be the result of a combination of improved cell extensibility and stimulated cell division attributable to arrest at the G1 phase of the cell cycle since cell development in the G1 phase is closely linked to shoot growth (Finkelstein et al 2002).…”

“…Exogenous ABA increased the formation of lateral roots. This may be due to the fact that ABA may transmit a Ca 2+ signal to cells in the epidermis and vascular cylinder either directly or indirectly, to alter cell fates (Chen et al 2006). Under lead stress, 2.5 mg L −1 ABA significantly increased root dry mass, R/S, and the number of lateral roots compared with Pb treatments alone, indicating that 2.5 mg L −1 ABA application partially counteracted the inhibitory effects of Pb on plant growth (Table 1).…”

“…ABA is a signal molecule and regulates many aspects of plant development and growth (Chen et al 2006). In most cases, the ABA-mediated responses in plants are associated with generation of H 2 O 2 (Jiang and Zhang 2002;Zhao et al 2009).…”