Abstract
Low temperature causes anther dysfunction, severe pollen sterility and, ultimately, major yield losses in crop plants. Previous studies have shown that the gibberellic acid (GA) metabolic pathway plays an important role in this process by regulating tapetum function and pollen development. However, the interaction mechanism of GA with other hormones mediating anther development is still unclear. Herein, we collected and analyzed almond (Amygdalus communis L.) anthers at the meiosis, tetrad, 1-nucleus, and mature 2-nucleus stages. The growth rate per 1000 anthers exhibited a significant positive correlation with the total bioactive GA compound content, and the levels of all bioactive GA compounds were highest in the 1-nucleus pollen stage. GA3 treatment experiments indicated that exogenous GA3 increased the levels of indole-3-acetic acid (IAA), trans-zeatin (tZ), and jasmonic acid (JA) and decreased the levels of salicylic acid (SA) and abscisic acid (ABA); moreover, GA3 improved pollen viability and quantities under cold conditions, whereas PP333 (paclobutrazol, an inhibitor of GA biosynthesis) was antagonistic with GA3 in controlling anther development. RNA-seq and qRT-PCR results showed that GA played an important role in anther development by regulating the expression of other phytohormone pathway genes, dehydration-responsive element-binding/C-repeat binding factor (DREB1/CBF)-mediated signaling genes, and anther development pathway genes. Our results reveal the novel finding that GA interacts with other hormones to balance anther development under normal- and low-temperature conditions in almond.
Highlights
A suitable temperature is a necessary condition for the survival of organisms, but the adaptability of various organisms to changes in temperature differs considerably[1]
The results showed that the growth rate per 1000 anthers was 0.10 mg/d in ZP1 (“Zhipi” almond at the meiosis stage in the field), 0.21 mg/d in ZP2 (“Zhipi” at the tetrad stage in the field), and 3.38 mg/d in ZP3 (“Zhipi” at the 1-nucleus stage in the field) and fell to 0.69 mg/d in ZP4 (“Zhipi” at the mature 2-nucleus stage in the field) (Table 1), indicating that rapid growth of anthers occurs from the tetrad stage to the 1-nucleus stage
We found that the levels of indole-3-acetic acid (IAA), tZ, and jasmonic acid (JA) were higher in GA3-treated anthers than in CK anthers, whereas there was no significant difference between PP333-treated and CK anthers
Summary
A suitable temperature is a necessary condition for the survival of organisms, but the adaptability of various organisms to changes in temperature differs considerably[1]. A significant difference between plants and other multicellular complex organisms is that plants live in a fixed state. Throughout their life cycle, plants are forced to endure a variety of adverse environmental conditions, among which low temperature is one. As an important hormone regulating anther development, gibberellic acid (GA) plays an important role in resisting chilling injury. Previous studies have shown that bioactive GAs (GA1, GA3, GA4, and GA7) function in pollen exine formation and programmed cell. Previous research has shown that the B3 domain-containing transcription factor FUS3 plays a role in controlling the GAABA balance[10] and that GA and abscisic acid (ABA) act antagonistically to control Arabidopsis development
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