Key transcription factors required for outburst of rice blast disease in Magnaporthe oryzae

Abstract

Rice blast is a serious threat to the safe production of grain crops such as rice and wheat. Sporulation, appressorium formation, and invasive growth of Magnaporthe oryzae are the key stages of the development and spread of rice blast epidemics. M. oryzae is a hemibiotrophic fungus that undergoes changes in available carbon sources during the infection cycle. Lipid is a major storage for M. oryzae spores and a major carbon source used in glycerol synthesis and turgor pressure generation in appressoria. The formation of a dense cell wall melanin layer is necessary for an appressorium to produce turgor and to be pathogenic. The plant cell wall is an important carbon source during the infection stage of M. oryzae. Transcription factors regulate gene expression in fungi and are key intermediates between the reception of external environmental signals and the control of development and pathogenicity in M. oryzae. The disease cycle of M. oryzae is controlled by some key transcription factors, such as sporulation by Cos1 and Hox2, appressorium formation by Sfl1, Hox7, and Vrf1, invasive growth by Mst12 and Mig1, and resistance to host basal immunity by Ap1 and Atf1. This review focuses on describing the key transcription factors of M. oryzae that regulate sporulation, appressorium formation, invasive growth, lipid metabolism, carbohydrate metabolism, melanin synthesis, oxidative response, and host basal immunity, as well as the working mechanism of the transcription factors.

The link between changing in host carbon allocation and resistance to Magnaporthe oryzae : a possible tactic for mitigating the rice blast fungus

“…The hemibiotrophic fungus M. oryzae changes its available carbon sources during the course of an infection. 66 Thus, the rice plant’s vulnerability to the rice blast fungus pathogen depends on the amount and distribution of carbon in the plant. 29 , 31 , 67 The fungus can use an abundance of carbon to fuel the growth and multiplication of infectious hyphae when there is a surplus of carbon present, such as during times of high photosynthetic activity or nutrient-rich conditions.…”

“…On the other hand, the M. oryzae pathogen may find it more difficult to infect and spread throughout the plant if there is a shortage of carbon due to stress or resource competition. 48 , 66 , 68 Plants with low levels of carbon source may display more robust defense mechanisms, such as the synthesis of defense compounds and the activation of genes linked to defense, which may aid in mitigating or preventing the effects of rice blast. 69 Thus, managing the rice blast requires an understanding of the balance of carbon allocation.…”