Temperature stress interferes with male reproductive system development in clementine (Citrus clementina Hort. ex. Tan.)

• Published in: Annals of applied biology 2019-07, Vol.175 (1), p.29-41
• Main Authors: Bennici, Stefania, Distefano, Gaetano, Las Casas, Giuseppina, Di Guardo, Mario, Lana, Giuseppe, Pacini, Ettore, La Malfa, Stefano, Gentile, Alessandra
• Format: Article
• Language: English
• Subjects: Agronomy; Anthers; Biological activity; Citrus clementina; climate change; Depletion; Endothecium; Environmental stress; Epidermis; Gametophytes; Germination; Global temperatures; Life cycles; Male sterility; microgametogenesis; Microspores; microsporogenesis; Morphology; Plant reproductive structures; Pollen; Reproductive system; Starch; sterility; Temperature effects; Variation
• ISSN: 0003-4746; 1744-7348
• DOI: 10.1111/aab.12508

Male gametophyte development is a critical phase of the plant life cycle due to its high sensitivity to environmental stresses. The rise in the average global temperature, often accompanied by extreme fluctuations, has an important impact on biological processes. Among those, male gametophytes are particularly sensitive to temperature stress during flower bud development and anthesis. Male gametophyte development was extensively studied in several plant species, but little information is available about the effects of temperature stress on male gametophyte development in the genus Citrus. We evaluated the effects of cold and hot temperatures during microsporogenesis and microgametogenesis on one of the most economically valuable citrus species, the “Comune” clementine (Citrus clementina Hort. ex. Tan.). The effect of constant temperature on the androecium was evaluated by a time course histological analysis performed on the anthers and by monitoring in vitro pollen germination. The results revealed how suboptimal hot and cold temperatures induce drastic alterations on the morphology of the tapetal cells, microspores and mature pollen grains. Shifting from the optimal temperature affected the timing of starch depletion in the anther walls, such as epidermis, endothecium and middle layer, influencing the pollen germination rate and pollen tube growth. To the best of our knowledge this is the first study attempting to assess how temperature stress affects male reproductive development in citrus. A better understanding of the mechanisms underlining male sterility will provide novel insights to elucidate the physiology of this agronomical important quality trait. Clementine anther tissues undergo important modifications during pollen development in response to both suboptimal hot and cold thermal conditions. These modifications affect the physiology and morphology of the tapetal cells, microspores, mature pollen grains and starch depletion affecting the pollen germination rate and pollen tube growth.