Begcy Kevin, Mondragón-Palomino Mariana, Zhou Liang-Zi, Seitz Patricia-Lena, Márton Mihaela-Luiza, Dresselhaus Thomas
Environmental Horticulture Department, University of Florida, Gainesville, FL 32611, USA.
Cell Biology and Plant Biochemistry, University of Regensburg, Regensburg 93040, Germany.
Plant Physiol. 2024 Dec 2;196(4):3071-3090. doi: 10.1093/plphys/kiae536.
During sexual reproduction in flowering plants, tip-growing pollen tubes travel from the stigma inside the maternal tissues of the pistil toward ovules. In maize (Zea mays L.), the stigma is highly elongated, forming thread-like strands known as silks. Only compatible pollen tubes successfully penetrate and grow through the transmitting tract of the silk to reach the ovules. Like pollen, fungal spores germinate at the surface of silks and generate tube-like structures (hyphae) penetrating silk tissue. To elucidate commonalities and differences between silk responses to these distinctive invading cells, we compared growth behavior of the various invaders as well as the silk transcriptome after self-pollination, cross-pollination, and infection using 2 different fungi. We report that self-pollination triggers mainly senescence genes, whereas incompatible pollen from Tripsacum dactyloides leads to downregulation of rehydration, microtubule, and cell wall-related genes, explaining the slower pollen tube growth and arrest. Invasion by the ascomycete Fusarium graminearum triggers numerous defense responses including the activation of monolignol biosynthesis and NAC as well as WRKY transcription factor genes, whereas responses to the basidiomycete Ustilago maydis are generally much weaker. We present evidence that incompatible pollination and fungal infection trigger transcriptional reprograming of maize silks cell wall. Pathogen invasion also activates the phytoalexin biosynthesis pathway.
在开花植物的有性生殖过程中，顶端生长的花粉管从雌蕊母体组织内的柱头向胚珠生长。在玉米（Zea mays L.）中，柱头高度伸长，形成线状的丝状物，称为花丝。只有亲和的花粉管才能成功穿透并通过花丝的传输通道到达胚珠。与花粉一样，真菌孢子在花丝表面萌发，并产生穿透花丝组织的管状结构（菌丝）。为了阐明花丝对这些不同入侵细胞反应的共性和差异，我们比较了不同入侵者的生长行为以及自花授粉、异花授粉和用两种不同真菌感染后花丝的转录组。我们报告说，自花授粉主要触发衰老基因，而来自大刍草的不亲和花粉会导致再水化、微管和细胞壁相关基因的下调，这解释了花粉管生长较慢和停滞的原因。子囊菌禾谷镰刀菌的入侵引发了许多防御反应，包括单木质醇生物合成以及NAC和WRKY转录因子基因的激活，而对担子菌玉米黑粉菌的反应通常要弱得多。我们提供的证据表明，不亲和授粉和真菌感染会触发玉米花丝细胞壁的转录重编程。病原体入侵还激活了植物抗毒素生物合成途径。
