Autophagy mitigates high-temperature injury in pollen development of Arabidopsis thaliana

Comprehensive Analysis of Autophagy-Related Genes in Sweet Orange (Citrus sinensis) Highlights Their Roles in Response to Abiotic Stresses

“…Most ATGs were first identified and functionally characterized by mutagenesis studies in yeast [2]. More than 30 ATGs have now been identified in yeast, and 23, including ATG1-10, [12][13][14][16][17][18]20,27,29,31,TOR,VPS15,and VPS34, are considered to be the core ATGs participating in autophagy [3,4]. In Arabidopsis, around 40 homologues to these core ATGs have been identified, except for ATG14, 17,27,29, and 31 with no homologues [1,3].…”

“…The first ATG gene was identified from yeast, and at least 32 ATGs have been shown to participate in yeast autophagy [5,6]. To date, many homologues of ATGs have been identified from various plant species, including 40 AtATGs in Arabidopsis [1,3] (Arabidopsis thaliana, At), 33 OsATGs in rice [7] (Oryza sativa, Os), 30 NtATGs in tobacco [8] (Nicotiana tabacum, Nt), 45 ZmATGs in maize [9] (Zea mays, Zm), 29 CaATGs in pepper [10] (Capsicum annuum, Ca), 37 SiATGs in foxtail millet [11] (Setaria italic, Si), 32 MaATGs in banana [12] (Musa acuminate, Ma), and 35 VvATGs in grapevine [13] (Vitis vinifera, Vv). According to the reported characterizations of ATGs in yeast and Arabidopsis, these ATGs can be divided into the following functional groups: (1) the ATG1/13 kinase complex consisting of ATG1, ATG13, ATG20, and TOR (target of rapamycin kinase), mainly functioning on autophagy induction and initiation; (2) the PI3K (phosphatidylinositol 3 kinase) complex consisting of ATG6, VPS15 (vacuolar protein sorting-associated protein), and VPS34 that is involved in vesicle nucleation and autophagosome formation; (3) the ATG9/2/18 complex consisting of ATG9, ATG2, and ATG18 that is responsible for the delivery of membranes for autophagosome formation; (4) the ubiquitin-like ATG8-PE (phosphatidylethanolamine) conjugation pathway (including ATG3, ATG4, ATG7, and ATG8) and ATG12-ATG5 conjugation pathway (including ATG5, ATG7, ATG10, ATG12, and ATG16) that are involved in the elongation of autophagic vesicles; and (5) the VTI12 (vesicle transport v-soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) protein) family belonging to the SNARE group, which contributes to the fusion of autophagosomes with vacuoles [1][2][3][4]6].…”

“…Under salt stress, autophagosome formation was rapidly induced, and the atg2 and atg7 mutants of Arabidopsis showed hypersensitive phenotype [28]. Under heat stress, atg mutants of Arabidopsis displayed visibly impaired pollen development (including atg2-1, atg5-1, atg7-2, and atg10-1) [29] or enhanced growth inhibition (including atg2-1, atg5-1, atg12ab, and atg18a-2) [30]. Recently, Shinozaki et al proved that autophagy played important role in maintaining zinc bioavailability to avoid ROS accumulation under zinc deficiency in Arabidopsis [31].…”

Autophagy: An Intracellular Degradation Pathway Regulating Plant Survival and Stress Response

“…Defective autophagy causes accumulation of these HSPs, suggesting that autophagy promotes the degradation of HSPs and unfolded proteins (Sedaghatmehr et al, 2019). Additionally, in Arabidopsis, hightemperature stress (30°C) promotes autophagy in both anther wall cells and microspores in developing anthers of plants, while atg mutants (atg2-1, atg5-1, atg7-2, and atg10-1) have visibly impaired pollen development and anther dehiscence, suggesting that autophagy functions in tapetum degeneration and pollen development during high-temperature stress (Dündar et al, 2019).…”

Boosting autophagy in sexual reproduction: a plant perspective

“…Although our current knowledge on the roles of autophagy in the differentiation and formation of plant sperm cells is limited, there are some studies showing that autophagic vacuole degradation participates in clearance of cytoplasm and organelles after the meiotic event to produce microspores and the subsequent mitotic event that leads to the formation of haploid gametophyte (McCue et al , ; Bárány et al , ; Pérez‐Pérez et al , ). The autophagic degradation of existing cellular components facilitates the rearrangement of the cytoplasm and formation of a new haploid nucleus in each microspore, which is essential for the transition from sporophyte to gametophyte (Zhao et al , ; Dündar et al , ). Ultrastructural analysis of the processes during lily pollen development and maturation showed that various types of organelles including endoplasmic reticulum, plastids, lipid globules and mitochondria were sent to the vacuole lumen for degradation (Pacini et al , ).…”