The APETALA-2-Like Transcription Factor OsAP2-39 Controls Key Interactions between Abscisic Acid and Gibberellin in Rice

Abstract

The interaction between phytohormones is an important mechanism which controls growth and developmental processes in plants. Deciphering these interactions is a crucial step in helping to develop crops with enhanced yield and resistance to environmental stresses. Controlling the expression level of OsAP2-39 which includes an APETALA 2 (AP2) domain leads to phenotypic changes in rice. Overexpression of OsAP2-39 leads to a reduction in yield by decreasing the biomass and the number of seeds in the transgenic rice lines. Global transcriptome analysis of the OsAP2-39 overexpression transgenic rice revealed the upregulation of a key Abscisic Acid (ABA) biosynthetic gene OsNCED-I which codes for 9-cis-epoxycarotenoid dioxygenase and leads to an increase in the endogenous ABA level. In addition to OsNCED-1, the gene expression analysis revealed the upregulation of a gene that codes for the Elongation of Upper most Internode (EUI) protein, an enzyme that catalyzes 16α, 17-epoxidation of non-13-hydroxylated GAs, which has been shown to deactivate gibberellins (GAs) in rice. The exogenous application of GA restores the wild-type phenotype in the transgenic line and ABA application induces the expression of EUI and suppresses the expression of OsAP2-39 in the wild-type line. These observations clarify the antagonistic relationship between ABA and GA and illustrate a mechanism that leads to homeostasis of these hormones. In vivo and in vitro analysis showed that the expression of both OsNCED-1 and EUI are directly controlled by OsAP2-39. Together, these results reveal a novel mechanism for the control of the ABA/GA balance in rice which is regulated by OsAP2-39 that in turn regulates plant growth and seed production.

Rice HOX12 Regulates Panicle Exsertion by Directly Modulating the Expression of ELONGATED UPPERMOST INTERNODE1

“…An important aspect of our findings is that HOX12 expression itself is stimulated by ABA, thereby constituting a positively acting ABA-HOX12-EUI1 activator loop for regulating cell expansion upon detection of external and internal signals. EUI1 activity is induced by endogenous and exogenous ABA and GA Yaish et al, 2010;Magome et al, 2013). AP2-39, encoding a member of the AP2 family, regulates key interactions between ABA and GA in rice.…”

Short Communication Proline accumulation is a general response to abiotic stress in the date palm tree (Phoenix dactylifera L.)

“…Thus, de novo production of ABA enhances both drought and salinity tolerance in some plant species. It is worth noting that in this regard, an overall increase of ABA did not necessarily always lead to improved drought tolerance since this increase is not consistent in all plant tissues and cell types, this includes the guard cells of the stomata that play a crucial role in plant drought tolerance (Yaish et al, 2010).…”

“…Plants then were watered, as needed, to field capacity for six weeks. Consequently, separate sets of six seedlings were either watered regularly (control treatment), watered twice with 300 mM NaCl solution over the course of the entire week (salinity shock), left without irrigation for two additional weeks (drought treatment), incubated overnight in the dark at 50°C (heat treatment) or 4°C (cold treatment), or had the leaves sprayed twice with 10 µM ABA as previously described (Yaish et al, 2010). In the cold and heat treatments, plants were covered with a plastic bag to prevent direct leaf dehydration.…”

Regulation of Histone Methylation and Reprogramming of Gene Expression in the Rice Inflorescence Meristem

“…These data confirmed the developmental stages of the collected meristem samples. Other transcription factor genes previously shown to be involved in panicle development were found to be upregulated, including MADS56 (Ryu et al, 2009), SPL14 (Jiao et al, 2010;Miura et al, 2010), EATB (Ethyleneresponsive factor Associated with Tillering and panicle Branching) (Qi et al, 2011), AP2-39 (Yaish et al, 2010), and the GATA C2C2 zinc finger transcription factor gene (Os05g50270) (Wang et al, 2009a). Conversely, other transcription factor genes, such as MADS23 and MADS27 (which are AGL17 homologs), and a few AP2 genes (AP22-106, AP2-125, and AP2-33/IDS1 [INDETERMINATE SPIKELET1]) (Lee and An, 2012) were found to be among the downregulated genes in IM (Table 1).…”